Fluorine-containing polymer, purification method, and radiation-sensitive resin composition

ABSTRACT

An object of the present invention is to provide a novel fluorine-containing polymer, a radiation-sensitive resin composition for liquid immersion lithography which contains the fluorine-containing polymer, which leads to a pattern having an excellent shape and excellent depth of focus, wherein the amount of an eluted component in a liquid for liquid immersion lithography such as water that comes in contact with the resist during exposure in liquid immersion lithography is little, and which provides a larger receding contact angle between the resist film and the liquid for liquid immersion lithography such as water, and a method for purifying the fluorine-containing polymer. The present resin composition comprises a novel fluorine-containing polymer (A) containing repeating units represented by the general formulae (1) and (2) and having Mw of 1,000-50,000, a resin (B) having an acid-unstable group, a radiation-sensitive acid generator (C), a nitrogen-containing compound (D) and a solvent (E).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/299,871, filed Oct. 21, 2016, which in turn is acontinuation application of U.S. patent application Ser. No. 14/933,641,filed Nov. 5, 2015, which in turn is a continuation application of U.S.patent application Ser. No. 14/178,622, filed Feb. 12, 2014, which inturn is a continuation application of U.S. patent application Ser. No.12/294,386, filed Jan. 26, 2009, which in turn is a national stage ofInternational Application No. PCT/JP2007/056094, filed Mar. 23, 2007,which claims priority to Japanese Patent Application No. 2006-099889,filed Mar. 31, 2006, Japanese Patent Application No. 2006-165310, filedJun. 14, 2006, Japanese Patent Application No. 2006-247299, filed Sep.12, 2006, and Japanese Patent Application No. 2007-010765, filed Jan.19, 2007. The contents of these applications are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a novel fluorine-containing polymerwhich is suitably used in a resist for liquid immersion lithography inwhich a resist film is exposed to light through a liquid for liquidimmersion lithography such as water, a purification method, and aradiation-sensitive resin composition.

BACKGROUND ART

In the field of microfabrication represented by the manufacture ofintegrated circuit devices, lithographic technology enablingmicrofabrication with 0.10 μm or less has been demanded in order toincrease the degree of integration in recent years. However,microfabrication in a subquarter micron level is said to be verydifficult using near ultraviolet rays such as i-lines which aregenerally used as radiation in a common lithography process. Therefore,in order to enable microfabrication with 0.10 μm or less, use ofradiation with a shorter wavelength is being studied. As examples ofsuch short wavelength radiations, bright line spectrum of a mercurylamp, deep ultraviolet rays represented by excimer lasers, X rays,electron beams, and the like can be given. A KrF excimer laser(wavelength: 248 nm) or an ArF excimer laser (wavelength: 193 nm) aregiven particular attention.

A number of resists (hereinafter referred to as “chemically-amplifiedresist”) utilizing a chemical amplification effect between a componenthaving an acid-dissociable functional group and a component (hereinafterreferred to as “acid generator”) which generates an acid upon beingexposed to radiation (hereinafter referred to as “exposure”) have beenproposed as a resist suitable for being exposed to such an excimerlaser. A chemically-amplified resist has been proposed which comprises aresin having t-butyl ester group of a carboxylic acid or t-butylcarbonate group of phenol and an acid generator. The t-butyl ester groupor t-butyl carbonate group in the resin dissociates by the function ofan acid generated upon exposure, whereby the resist has an acidic groupsuch as a carboxyl group or a phenolic hydroxyl group. As a result,exposed areas on the resist film become readily soluble in an alkalinedeveloper.

Formation of more minute patterns (a minute resist pattern with a linewidth of about 45 nm, for example) will be required for such alithographic process in the future. Reducing the wavelength of a lightsource of a photolithography instrument and increasing the numericalaperture (NA) of a lens are thought to be means for forming such apattern with less than 45 nm, as described above. However, an expensiveexposure machine is necessary for reducing the wavelength of a lightsource. In addition, increasing the numerical aperture (NA) of a lensinvolves a problem of decreasing the depth of focus even if resolutionis increased due to a trade-off relationship between the resolution andthe depth of focus.

Recently, a liquid immersion lithographic process has been reported as alithographic technique enabling a solution for such a problem. In theliquid immersion lithographic process, a liquid refractive-index medium(liquid for liquid immersion lithography) such as pure water and afluorine-containing inert liquid is caused to be present between a lensand a resist film on a substrate while having a specified thickness, atleast on the surface of the resist film. In this method, when air or aninert gas such as nitrogen in a light-path is replaced by a liquidhaving a larger refractive index (n) such as pure water, the resolutioncan be increased without a decrease in depth of focus by using a lightsource with a given wavelength to the same degree as in the case inwhich a light source with a shorter wavelength is used, or the case inwhich a higher NA lens is used. Since a resist pattern having a higherresolution and excellent depth of focus can be formed at a low costusing the lens mounted on existing apparatuses by utilizing the liquidimmersion lithography, the liquid immersion lithography has gotten agreat deal of attention.

In the above-mentioned liquid immersion lithographic process, however,an acid generator and the like is eluted from the resist film since theresist film is brought into direct contact with the liquid for liquidimmersion lithography such as water during exposure. When a large amountof the components is eluted, the lens may be damaged, a pattern having aprescribed shape may not be obtained, and a sufficient resolution maynot be obtained.

Additionally, in the case where water is used as the liquid for liquidimmersion lithography, water may not be sufficiently removed during highspeed scanning exposure and watermarks may be left, if a recedingcontact angle between the resist film and water is small.

Resins described in Patent Document 1 and Patent Document 2, andadditives described in Patent Document 3 have been proposed as a resinfor using in a liquid immersion lithographic apparatus.

However, the receding contact angle between the resist and water is notnecessarily sufficient in resists in which these resins and additivesare used. A small receding contact angle tends to leave watermarks dueto poor water removal during high speed scanning exposure. Moreover, theproposed resists do not necessarily sufficiently suppress elution of anacid generator and the like in water.

[Patent Document 1] WO 2004/068242

[Patent Document 2] JP-A 2005-173474

[Patent Document 3] JP-A 2006-48029

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

An object of the present invention is to provide a novelfluorine-containing polymer, a radiation-sensitive resin composition forliquid immersion lithography which contains the fluorine-containingpolymer, which leads to a pattern having an excellent shape andexcellent depth of focus, wherein the amount of an eluted component in aliquid for liquid immersion lithography such as water that comes incontact with the resist during exposure in liquid immersion lithographyis little, and which provides a larger receding contact angle betweenthe resist film and the liquid for liquid immersion lithography such aswater, and a method for purifying the fluorine-containing polymer.

Means for Solving the Problems

The means for attaining the above-mentioned objective are as follows.

[1] A fluorine-containing polymer for use in a radiation-sensitive resincomposition which is used for forming a photoresist film in a process offorming a resist pattern, including a liquid immersion lithographicprocess in which radiation is emitted through a liquid having arefractive index larger than the refractive index of air at a wavelengthof 193 nm, and being present between a lens and the photoresist film,characterized in that the fluorine-containing polymer has a weightaverage molecular weight determined by gel permeation chromatography inthe range from 1,000 to 50,000 and a receding contact angle with waterand the photoresist film formed therefrom is 70° or more.[2] The fluorine-containing polymer according to above [1], comprising arepeating unit represented by the following general formula (1),

wherein R¹ represents hydrogen atom, methyl group or a trifluoromethylgroup, A represents a connecting group, and R² represents a linear orbranched alkyl group having 1 to 6 carbon atoms or a monovalentalicyclic hydrocarbon group having 4 to 20 carbon atoms, each containingat least one fluorine atom, or a derivative thereof.[3] The fluorine-containing polymer according to above [1] or [2],comprising a repeating unit represented by the following general formula(2),

wherein R³ represents hydrogen atom, methyl group or a trifluoromethylgroup, and R⁴ individually represents a monovalent alicyclic hydrocarbongroup having 4 to 20 carbon atoms or a derivative thereof, or a linearor branched alkyl group having 1 to 4 carbon atoms.[4] A radiation-sensitive resin composition characterized by comprisingthe fluorine-containing polymer (A) according to any one of Claims [1]to [3], a resin (B) having an acid-unstable group, a radiation-sensitiveacid generator (C), a nitrogen-containing compound (D) and a solvent(E).[5] The radiation-sensitive resin composition according to above [4],wherein the content of the fluorine-containing polymer (A) is 0.1% ormore by weight based on 100% by weight of the whole of theradiation-sensitive resin composition.[6] The radiation-sensitive resin composition according to above [4] or[5], wherein the resin (B) comprises a repeating unit having a lactonestructure.[7] The radiation-sensitive resin composition according to any one ofabove [4] to [6], wherein the acid-unstable group of the resin (B) has amonocyclic structure or a polycyclic structure.[8] A method for purifying the fluorine-containing polymer according toany one of above [1] to [3], characterized by contacting a resinsolution in which the fluorine-containing polymer is dissolved in thefollowing solvent C with the following solvent A to a homogeneoussolution, bringing the resin solution into contact with the followingsolvent B, and then with water,Solvent A: A hydrocarbon solvent having 5 to 10 carbon atomsSolvent B: An alcoholic solvent having 1 to 10 carbon atoms which isinsoluble in solvent ASolvent C: A ketone solvent having 2 to 10 carbon atoms which is solublein solvent A and solvent B.

Effect of the Invention

When the radiation-sensitive resin composition for liquid immersionlithography comprising the specific fluorine-containing polymer of thepresent invention is used, a resultant pattern is favorable, depth offocus is excellent, and the amount of components eluted in a liquid withwhich the resist comes in contact during exposure by liquid immersionlithography can be minimized. Furthermore, the receding contact anglebetween the resist film and the liquid for liquid immersion lithographycan be sufficiently increased to ensure complete removal of water dropsduring high speed scanning exposure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing for explanation of the method of preparinga sample for measuring eluted amount.

FIG. 2 is a cross-sectional view of a line and space pattern.

EXPLANATION OF SYMBOLS

1; substrate, 2; pattern, 3; silicon wafer, 31; HMDS, 4; silicon rubbersheet, 5; ultra pure water, 6; silicon wafer, 61; anti-reflection film,62; resist film.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention is described in detail.

<Fluorine-Containing Polymer (A)>

The fluorine-containing polymer (A) (hereinafter referred to simply as“polymer (A)”) in the present invention is a polymer for formulatinginto a radiation-sensitive resin composition for forming a resist filmin a process of forming a resist pattern, including a liquid immersionlithographic process in which radiation is emitted through a liquidhaving a refractive index larger than the refractive index of air at awavelength of 193 nm, and being present between a lens and the resistfilm, and leads to a receding contact angle between water and the resistfilm formed therefrom of 70° or more.

The receding contact angle is more preferably 75° or more, still morepreferably 80° or more, and particularly preferably 85° or more. Theterm “receding contact angle” in the present specification refers to acontact angle between a liquid surface and a substrate on which a filmof a resin composition containing the polymer (A) is formed, when 25 μLof water is dropped on the substrate and thereafter suctioned at a rateof 10 μL/min. The receding contact angle can be measured using “DSA-10”(manufactured by KRUS) as described later in Examples.

Since the polymer (A) has fluorine sites in the structure, thedistribution of the polymer (A) tends to be high near the surface of theresist film formed from the resist composition to which the polymer (A)is added due to the oil repellence of the polymer (A), whereby elutionof an acid generator, an acid diffusion controller and the like in theliquid for liquid immersion lithography such as water during exposurecan be suppressed. In addition, the receding contact angle between theresist film and the liquid for liquid immersion lithography is increaseddue to the water repellence of the polymer (A), which ensures high speedscanning exposure without leaving waterdrops. Moreover, if a commonupper layer film for liquid immersion lithography is used incombination, not only elution can be further reduced, but also defectssuch as watermarks which are caused by the liquid for liquid immersionlithography can be suppressed due to high water repellency in theresist.

The polymer (A) according to the present invention is produced bypolymerizing at least one monomer having fluorine atom in the structure.

Examples of the monomer having fluorine atom in the structure include amonomer having fluorine atom in the main chain, a monomer havingfluorine atom in side chains, and a monomer having fluorine atom in themain chain and side chain.

Examples of the monomer having fluorine atom in the main chain includean α-fluoroacrylate compound, an α-trifluoromethyl acrylate compound, aβ-fluoroacrylate compound, a β-trifluoromethyl acrylate compound, an α,β-fluoroacrylate compound, an α, β-trifluoromethyl acrylate compound, acompound in which hydrogen atom on one or more vinyl sites issubstituted with fluorine atom, a trifluoromethyl group or the like, andthe like.

In addition, examples of the monomer having fluorine atom in the sidechain include an alicyclic olefin compound such as norbornene of whichthe side chain comprises fluorine atom, a fluoroalkyl group or aderivative thereof, an ester compound having a fluoroalkyl group or aderivative thereof of acrylic acid or methacrylic acid, one or moreolefins of which the side chain (positions not containing a double bond)is fluorine atom, a fluoroalkyl group or a derivative thereof, and thelike.

Examples of the monomer having fluorine atoms in the main chain and sidechain include an ester compound having a fluoroalkyl group or aderivative thereof such as α-fluoroacrylic acid, β-fluoroacrylic acid,α,β-fluoroacrylic acid, α-trifluoromethylacrylic acid,β-trifluoromethylacrylic acid and α,β-trifluoromethylacrylic acid; acompound derived by substituting a side chain of a compound in whichhydrogen atom on one or more of vinyl site is substituted with fluorineatom, trifluoromethyl group or the like, with fluorine atom, afluoroalkyl group or a derivative thereof; a compound derived byreplacing hydrogen atom bonded to a double bond of one or more alicyclicolefin compounds with fluorine atom, trifluoromethyl group or the like,and of which the side chain is a fluoroalkyl group or a derivativethereof; and the like. The term “alicyclic olefin compound” refers to acompound having a double bond in the ring.

Although the repeating unit providing the polymer (A) having fluorineatom is not particularly limited as mentioned above, the repeating unitrepresented by the following general formula (1) (hereinafter referredto as “repeating unit (1)”) is preferably used as a fluorine-impartingrepeating unit.

[In the general formula (1), R¹ represents hydrogen atom, methyl groupor a trifluoromethyl group, A represents a connecting group, and R²represents a linear or branched alkyl group having 1 to 6 carbon atomsor a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms,each containing at least one fluorine atom, or a derivative thereof.]

A in the general formula (1) represents a connecting group and examplesthereof include a single bond, an oxygen atom, a sulfur atom, acarbonyloxy group, an oxycarbonyl group, an amide group, a sulfonylamidegroup, a urethane group and the like.

Examples of the linear or branched alkyl group having 1 to 6 carbonatoms containing at least one fluorine atom represented by R² in thegeneral formula (1) include a partially fluorinated linear or branchedalkyl group such as methyl group, ethyl group, 1-propyl group, 2-propylgroup, 1-butyl group, 2-butyl group, 2-(2-methylpropyl) group, 1-pentylgroup, 2-pentyl group, 3-pentyl group, 1-(2-methylbutyl) group,1-(3-methylbutyl) group, 2-(2-methylbutyl) group, 2-(3-methylbutyl)group, neopentyl group, 1-hexyl group, 2-hexyl group, 3-hexyl group,1-(2-methylpentyl) group, 1-(3-methylpentyl) group, 1-(4-methylpentyl)group, 2-(2-methylpentyl) group, 2-(3-methylpentyl) group,2-(4-methylpentyl) group, 3-(2-methylpentyl) group and3-(3-methylpentyl) group, a perfluoroalkyl group and the like.

In addition, examples of the monovalent alicyclic hydrocarbon grouphaving 4 to 20 carbon atoms containing at least one fluorine atom or aderivative thereof represented by R² in the general formula (1) includea partially fluorinated alicyclic alkyl group such as cyclopentyl group,cyclopentylmethyl group, 1-(1-cyclopentylethyl) group,1-(2-cyclopentylethyl) group, cyclohexyl group, cyclohexylmethyl group,1-(1-cyclohexylethyl) group, 1-(2-cyclohexylethyl) group, cycloheptylgroup, cycloheptylmethyl group, 1-(1-cycloheptylethyl) group,1-(2-cycloheptylethyl) group, and 2-norbornyl group, a perfluoroalkylgroup and the like.

Preferable examples of the monomer which leads to the repeating unit (1)include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl(meth)acrylate, perfluoroethyl (meth)acrylate, perfluoro-n-propyl(meth)acrylate, perfluoro-i-propyl (meth)acrylate, perfluoro-n-butyl(meth)acrylate, perfluoro-i-butyl (meth)acrylate, perfluoro t-butyl(meth)acrylate, 2-(1,1,1,3,3,3-hexafluoropropyl) (meth)acrylate,1-(2,2,3,3,4,4,5,5-octafluoropentyl) (meth)acrylate,perfluorocyclohexylmethyl (meth)acrylate,1-(2,2,3,3,3-pentafluoropropyl) (meth)acrylate,1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)(meth)acrylate, 1-(5-trifluoromethyl-3,3,4,4,5,6,6,6-octafluorohexyl)(meth)acrylate and the like.

The above-mentioned polymer (A) may have one or more of these repeatingunits (1).

The content of the repeating unit (1) is usually 5 mol % or more,preferably 10 mol % or more, and more preferably 15 mol % or more basedon 100 mol % of the total amount of the repeating units in the polymer(A). If the content of the repeating unit (1) is less than 5 mol %, areceding contact angle at 70° or more may not be achieved and elution ofan acid generator and the like from a resist film may not be suppressed.

The polymer (A) according to the present invention preferably furthercomprises at least one repeating unit represented by the followinggeneral formula (2) (hereinafter referred to as “repeating unit (2)”).Inclusion of the repeating unit (2) ensures a high receding contactangle during exposure and increases solubility in alkaline duringdevelopment. Specifically, the polymer (A) maintains the structure ofthe general formula (2) during exposure, ensuring a high recedingcontact angle without an almost no loss of the effect of the monomerhaving fluorine atom in its structure, and thereafter releases —C(R⁴)₃group from the structure of the general formula (2), whereupon thesolubility of the polymer in alkaline is improved.

[In the general formula (2), R³ represents hydrogen atom, methyl groupor a trifluoromethyl group, and R⁴ individually represents a monovalentalicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivativethereof, or a linear or branched alkyl group having 1 to 4 carbonatoms.]

Examples of the monovalent alicyclic hydrocarbon group having 4 to 20carbon atoms represented by R⁴ in the general formula (2) include agroup comprising an alicyclic ring originated from a cycloalkane such asnorbornane, tricyclodecane, tetracyclododecane, adamantane, cyclobutane,cyclopentane, cyclohexane, cycloheptane and cyclooctane; and a groupobtained by substituting the alicyclic ring with one or more linear,branched or cyclic alkyl groups having 1 to 4 carbon atoms such asmethyl group, ethyl group, n-propyl group, i-propyl group, n-butylgroup, 2-methylpropyl group, 1-methylpropyl group and t-butyl group; andthe like. Two R⁴s may form a divalent alicyclic hydrocarbon group or aderivative thereof in combination of the carbon atoms to which these twogroups bond.

Among these alicyclic hydrocarbon groups, a group comprising analicyclic ring originated from an alicyclic group originated fromnorbornane, tricyclodecane, tetracyclododecane, adamantane, cyclopentaneor cyclohexane, a group in which a group comprising the alicyclic ringis substituted with the above alkyl groups, and the like are preferable.

Additionally, examples of the linear or branched alkyl group having 1 to4 carbon atoms represented by R⁴ in the general formula (2) includemethyl group, ethyl group, n-propyl group, i-propyl group, n-butylgroup, 2-methylpropyl group, 1-methylpropyl group, t-butyl group and thelike.

Preferable examples of the —C(R⁴)₃ in the general formula (2) includet-butyl group, 1-n-(1-ethyl-1-methyl)propyl group,1-n-(1,1-dimethyl)propyl group, 1-n-(1,1-dimethyl)butyl group,1-n-(1,1-dimethyl)pentyl group, 1-(1,1-diethyl)propyl group,1-n-(1,1-diethyl)butyl group, 1-n-(1,1-diethyl)pentyl group,1-(1-methyl)cyclopentyl group, 1-(1-ethyl)cyclopentyl group,1-(1-n-propyl)cyclopentyl group, 1-(1-i-propyl)cyclopentyl group,1-(1-methyl)cyclohexyl group, 1-(1-ethyl)cyclohexyl group,1-(1-n-propyl)cyclohexyl group, 1-(1-i-propyl)cyclohexyl group,1-{1-methyl-1-(2-norbornyl)}ethyl group,1-{1-methyl-1-(2-tetracyclodecanyl)}ethyl group,1-{1-methyl-1-(1-adamantyl)}ethyl group, 2-(2-methyl)norbornyl group,2-(2-ethyl)norbornyl group, 2-(2-n-propyl)norbornyl group,2-(2-i-propyl)norbornyl group, 2-(2-methyl)tetracyclodecanyl group,2-(2-ethyl)tetracyclodecanyl group, 2-(2-n-propyl)tetracyclodecanylgroup, 2-(2-i-propyl)tetracyclodecanyl group, 1-(1-methyl)adamantylgroup, 1-(1-ethyl)adamantyl group, 1-(1-n-propyl)adamantyl group and1-(1-i-propyl)adamantyl group; a group obtained by substituting analicyclic group with one or more linear, branched or cyclic alkyl groupshaving 1 to 4 carbon atoms such as methyl group, ethyl group, n-propylgroup, i-propyl group, n-butyl group, 2-methylpropyl group,1-methylpropyl group and t-butyl group; and the like.

Preferable examples of the monomer which leads to the repeating unit (2)include 2-methyladamantyl-2-yl (meth)acrylate,2-methyl-3-hydroxyadamantyl-2-yl (meth)acrylate, 2-ethyladamantyl-2-yl(meth)acrylate, 2-ethyl-3-hydroxyadamantyl-2-yl (meth)acrylate,2-n-propyladamantyl-2-yl (meth)acrylate, 2-isopropyladamantyl-2-yl(meth)acrylate, 2-methylbicyclo[2.2.1]hept-2-yl (meth)acrylate,2-ethylbicyclo[2.2.1]hept-2-yl (meth)acrylate,8-methyltricyclo[5.2.1.0^(2,6)]decan-8-yl (meth)acrylate,8-ethyltricyclo[5.2.1.0^(2,6)]decan-8-yl (meth)acrylate,4-methyltetracyclo[6.2.1^(3,6).0^(2,7)]dodecan-4-yl (meth)acrylate,4-ethyltetracyclo[6.2.1^(3,6).0^(2,7)]dodecan-4-yl (meth)acrylate,1-(bicyclo[2.2.1]hept-2-yl)-1-methylethyl (meth)acrylate,1-(tricyclo[5.2.1.0^(2,6)]decan-8-yl)-1-methylethyl (meth)acrylate,1-(tetracyclo[6.2.1^(3,6).0^(2,7)]dodecan-4-yl)-1-methylethyl(meth)acrylate, 1-(adamantan-1-yl)-1-methylethyl (meth)acrylate,1-(3-hydroxyadamantan-1-yl)-1-methylethyl (meth)acrylate,1,1-dicyclohexylethyl (meth)acrylate,1,1-di(bicyclo[2.2.1]hept-2-yl)ethyl (meth)acrylate,1,1-di(tricyclo[5.2.1.0^(2,6)]decan-8-yl)ethyl (meth)acrylate,1,1-di(tetracyclo[6.2.1^(3,6).0^(2,7)]dodecan-4-yl)ethyl (meth)acrylate,1,1-di(adamantan-1-yl)ethyl (meth)acrylate, 1-methyl-1-cyclopentyl(meth)acrylate, 1-ethyl-1-cyclopentyl (meth)acrylate,1-methyl-1-cyclohexyl (meth)acrylate, 1-ethyl-1-cyclohexyl(meth)acrylate and the like.

Of these monomers, 2-methyladamantyl-2-yl (meth)acrylate,2-ethyladamantyl-2-yl (meth)acrylate, 2-methylbicyclo[2.2.1]hept-2-yl(meth)acrylate, 2-ethylbicyclo[2.2.1]hept-2-yl (meth)acrylate,1-(bicyclo[2.2.1]hept-2-yl)-1-methylethyl (meth)acrylate,1-(adamantan-1-yl)-1-methylethyl (meth)acrylate, 1-methyl-1-cyclopentyl(meth)acrylate, 1-ethyl-1-cyclopentyl (meth)acrylate,1-methyl-1-cyclohexyl (meth)acrylate, 1-ethyl-1-cyclohexyl(meth)acrylate and the like are particularly preferred.

The above-mentioned polymer (A) may have one or more of these repeatingunits (2).

The content of the repeating unit (2) is usually 95 mol % or less,preferably 10 mol % to 90 mol %, and more preferably 10 mol % to 85 mol% based on 100 mol % of the total amount of the repeating units in thepolymer (A). If the content of the repeating unit (2) is more than 95mol %, a receding contact angle at 70° or more may not be achieved andelution of an acid generator and the like from a resist film may not besuppressed.

The polymer (A) may comprise one or more of “other repeating unit” suchas a repeating unit having a lactone skeleton, hydroxyl group andcarboxyl group to improve alkali solubility, a repeating unitoriginating from an alicyclic compound and a repeating unit originatingfrom an aromatic compound to improve etching resistance, and a repeatingunit originating from an aromatic compound to suppress reflection at asubstrate, in addition to the above-mentioned repeating unit havingfluorine atom in the structure and the repeating unit (2).

Examples of a monomer which leads to a repeating unit having a lactoneskeleton (hereinafter referred to as “repeating unit (3)”) include thefollowing compound represented by the general formulas (3-1) to (3-6),and the like.

In the general formulas (3-1) to (3-6), R⁵ represents hydrogen atom ormethyl group, R⁶ represents an alkyl group having 1 to 4 carbon atoms,that may be substituted, and R⁷ represents hydrogen atom or methoxygroup. Additionally, A represents a single bond or methylene group, Brepresents oxygen atom or methylene group. Further, l is an integer of 1to 3, and m is 0 or 1.

Examples of the alkyl group having 1 to 4 carbon atoms that may besubstituted as R⁶ in the general formula (3-1) include methyl group,ethyl group, n-propyl group, i-propyl group, n-butyl group,2-methylpropyl group, 1-methylpropyl group, t-butyl group and the like.

Preferable examples of the monomer which leads to the repeating unit (3)include 5-oxo-4-oxa-tricyclo[4.2.1.0^(3,7)]non-2-yl (meth)acrylate,9-methoxycarbonyl-5-oxo-4-oxa-tricyclo[4.2.1.0^(3,7)]non-2-yl(meth)acrylate, 5-oxo-4-oxa-tricyclo[5.2.1.0^(3,8)]dec-2-yl(meth)acrylate,10-methoxycarbonyl-5-oxo-4-oxa-tricyclo[5.2.1.0^(3,8)]non-2-yl(meth)acrylate, 6-oxo-7-oxa-bicyclo[3.2.1]oct-2-yl (meth)acrylate,4-methoxycarbonyl-6-oxo-7-oxa-bicyclo[3.2.1]oct-2-yl (meth)acrylate,7-oxo-8-oxa-bicyclo[3.3.1]oct-2-yl (meth)acrylate,4-methoxycarbonyl-7-oxo-8-oxa-bicyclo[3.3.1]oct-2-yl (meth)acrylate,2-oxotetrahydropyran-4-yl (meth)acrylate,4-methyl-2-oxotetrahydropyran-4-yl (meth)acrylate,4-ethyl-2-oxotetrahydropyran-4-yl (meth)acrylate,4-propyl-2-oxotetrahydropyran-4-yl (meth)acrylate,5-oxotetrahydrofuran-3-yl (meth)acrylate,2,2-dimethyl-5-oxotetrahydrofuran-3-yl (meth)acrylate,4,4-dimethyl-5-oxotetrahydrofuran-3-yl (meth)acrylate,2-oxotetrahydrofuran-3-yl (meth)acrylate,4,4-dimethyl-2-oxotetrahydrofuran-3-yl (meth)acrylate,5,5-dimethyl-2-oxotetrahydrofuran-3-yl (meth)acrylate,2-oxotetrahydrofuran-3-yl (meth)acrylate, 5-oxotetrahydrofuran-2-ylmethyl (meth)acrylate, 3,3-dimethyl-5-oxotetrahydrofuran-2-yl methyl(meth)acrylate, 4,4-dimethyl-5-oxotetrahydrofuran 2-yl methyl(meth)acrylate and the like.

Examples of the repeating unit containing an alicyclic compound(hereinafter referred to as “repeating unit (4)”) include a repeatingunit represented by the following general formula (4) and the like.

[In the general formula (4), R⁸ represents hydrogen atom, methyl groupor a trifluoromethyl group, and X represents an alicyclic hydrocarbongroup having 4 to 20 carbon atoms.]

Examples of the alicyclic hydrocarbon group having 4 to 20 carbon atomsas X in the general formula (4) include a hydrocarbon group containingan alicyclic ring originating from a cycloalkane such as cyclobutane,cyclopentane, cyclohexane, bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane,tricyclo[5.2.1.0^(2,6)]decane, tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecaneand tricycle[3.3.1.1^(3,7)]decane can be given.

These alicyclic rings originating from the cycloalkane may besubstituted with one or more linear, branched or cyclic alkyl groupshaving 1 to 4 carbon atoms such as methyl group, ethyl group, n-propylgroup, i-propyl group, n-butyl group, 2-methylpropyl group,1-methylpropyl group and a t-butyl group. These are not limited to onessubstituted with the above alkyl groups and may be substituted withhydroxyl group, cyano group, a hydroxyalkyl group having 1 to 10 carbonatoms, carboxyl group or oxygen atom.

Preferable examples of the monomer which leads to the repeating unit(4), bicyclo[2.2.1]hept-2-yl (meth)acrylate, bicyclo[2.2.2]oct-2-yl(meth)acrylate, tricyclo[5.2.1.0^(2,6)]dec-7-yl (meth)acrylate,tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-9-yl (meth)acrylate,tricyclo[3.3.1.1^(3,7)]dec-1-yl (meth)acrylate,tricyclo[3.3.1.1^(3,7)]dec-2-yl (meth)acrylate and the like.

Preferable examples of the monomer which leads to a repeating unitoriginating from an aromatic compound (hereinafter referred to as“repeating unit (5)”) include styrene, α-methylstyrene, 2-methylstyrene,3-methylstyrene, 4-methylstyrene, 2-methoxystyrene, 3-methoxystyrene,4-methoxystyrene, 4-(2-t-butoxycarbonylethyloxy)styrene,2-hydroxystyrene, 3-hydroxystyrene, 4-hydroxystyrene,2-hydroxy-α-methylstyrene, 3-hydroxy-α-methylstyrene,4-hydroxy-α-methylstyrene, 2-methyl-3-hydroxystyrene,4-methyl-3-hydroxystyrene, 5-methyl-3-hydroxystyrene,2-methyl-4-hydroxystyrene, 3-methyl-4-hydroxystyrene,3,4-dihydroxystyrene, 2,4,6-trihydroxystyrene, 4-t-butoxystyrene,4-t-butoxy-α-methylstyrene, 4-(2-ethyl-2-propoxy)styrene,4-(2-ethyl-2-propoxy)-α-methylstyrene, 4-(1-ethoxyethoxy)styrene,4-(1-ethoxyethoxy)-α-methylstyrene, phenyl (meth)acrylate, benzyl(meth)acrylate, acenaphthylene, 5-hydroxyacenaphthylene,1-vinylnaphthalene, 2-vinylnaphthalene, 2-hydroxy-6-vinylnaphthalene,1-naphthyl (meth)acrylate, 2-naphthyl (meth)acrylate, 1-naphthylmethyl(meth)acrylate, 1-anthryl (meth)acrylate, 2-anthryl (meth)acrylate,9-anthryl (meth)acrylate, 9-anthrylmethyl (meth)acrylate, 1-vinylpyreneand the like.

Either one type or two or more types of the “other repeating unit”represented by the repeating units (3) (4), and (5) may be included inthe polymer (A) according to the present invention.

The content of the other repeating unit is usually 70 mol % or less,preferably 65 mol % or less, and more preferably 60 mol % or less of thetotal amount of the repeating units in the polymer (A). If the contentof the other repeating unit is more than 70 mol %, a receding contactangle at 700 or more may not be achieved and elution of an acidgenerator and the like from a resist film may not be suppressed.

The fluorine-containing polymer (A) according to the present inventioncan be produced by polymerizing polymerizable unsaturated monomerscorresponding to each repeating unit in the presence of a chain transferagent as required, using a radical polymerization initiator such as ahydroperoxide, a dialkyl peroxide, a diacyl peroxide, and an azocompound in an appropriate solvent.

Examples of the solvent used for polymerization include an alkane suchas n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane; acycloalkane such as cyclohexane, cycloheptane, cyclooctane, decalin andnorbornane; an aromatic hydrocarbon such as benzene, toluene, xylene,ethylbenzene and cumene; a halogenated hydrocarbon such aschlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromideand chlorobenzene; a saturated carboxylic acid ester such as ethylacetate, n-butyl acetate, i-butyl acetate and methyl propionate; aketone such as 2-butanone, 4-methyl-2-pentanone and 2-heptanone; anether such as tetrahydrofuran, dimethoxyethanes and diethoxyethanes; analcohol such as methanol, ethanol, 1-propanol, 2-propanol and4-methyl-2-pentanol; and the like. These solvents may be used singly orin combination of two or more thereof.

The polymerization temperature is usually in the range from 40° C. to150° C., and preferably from 50° C. to 120° C. The reaction time isusually in the range from 1 to 48 hours, and preferably from 1 to 24hours.

Additionally, the polystyrene-reduced weight average molecular weightdetermined by gel permeation chromatography (GPC) (hereinafter referredto as “Mw”) of the fluorine-containing polymer (A) according to thepresent invention is in the range from 1,000 to 50,000, preferably 1,000to 40,000, and more preferably 1,000 to 30,000. If the Mw of the polymer(A) is less than 1,000, a sufficient receding contact angle cannot beobtained. On the other hand, if the Mw is more than 50,000,developability in a resist tends to be decreased.

The ratio (Mw/Mn) of the Mw to the polystyrene-reduced number averagemolecular weight of the polymer (A) (referred to as “Mn”) is normally inthe range from 1 to 5, and preferably 1 to 4.

In the polymer (A), the solids content of the low molecular weightcomponents originating from monomers used for preparing the polymer (A)is preferably 0.1% or less by weight, more preferably 0.07% or less byweight, and still more preferably 0.05% or less by weight based on 100%by weight of the polymer. If the content is less than 0.1% by weight,the eluted amount in the liquid for liquid immersion lithography such aswater with which the resist film comes in contact during exposure can bereduced. In addition, it is possible to prevent generation of extraneoussubstances in the resist during storage, inhibit uneven resistapplication, and sufficiently suppress defects during pattern formation.

Examples of the above-mentioned low molecular weight componentsoriginating from the monomers include a monomer, a dimer, a trimer andan oligomer, and they may be ones having Mw of 500 or less. Thecomponent having Mw of 500 or less can be removed by the purificationmethod to be described. The amount of the low molecular weightcomponents can be determined by analysis of the resin using highperformance liquid chromatography (HPLC).

It is preferable that the polymer (A) contain almost no impuritiescomprising halogens or metals. That can provide a resist leading toimproved sensitivity, resolution, process stability, pattern shape andthe like.

The polymer (A) can be purified by a chemical purification method suchas washing with water and liquid-liquid extraction, a combination of thechemical purification method and a physical purification method such asultrafiltration and centrifugation, or the like. Among the chemicalpurification methods, liquid-liquid extraction is particularlypreferred.

When the fluorine-containing polymer is purified by the liquid-liquidextraction, it is preferable that a resin solution (copolymer solution)in which the fluorine-containing polymer is dissolved in the followingsolvent C and the following solvent A are subjected to contact to ahomogeneous solution, the mixture is allowed to contact with thefollowing solvent B, and then with water.

Solvent A: A hydrocarbon solvent having 5 to 10 carbon atoms

Solvent B: An alcoholic solvent having 1 to 10 carbon atoms which isinsoluble in solvent A

Solvent C: A ketone solvent having 2 to 10 carbon atoms which is solublein solvent A and solvent B

Examples of the solvent A (hydrocarbon solvent having 5 to 10 carbonatoms) include an alkane such as n-pentane, n-hexane, n-heptane,n-octane, n-nonane and n-decane. Among these, n-hexane and n-heptane arepreferable. These solvents may be used singly or in combination of twoor more thereof.

Examples of the solvent B (alcoholic solvent having 1 to 10 carbon atomswhich is insoluble in solvent A) include an alcohol such as methanol,ethanol, 1-propanol, 2-propanol and 4-methyl-2-pentanol. Among these,methanol and ethanol are preferable. These solvents may be used singlyor in combination of two or more thereof.

Examples of the solvent C (ketone solvent having 2 to 10 carbon atomswhich is soluble in solvent A and solvent B) include a ketone such asacetone, 2-butanone, 4-methyl-2-pentanone and 2-heptanone. Among these,acetone and 2-butanone are preferable. These solvents may be used singlyor in combination of two or more thereof.

Preferable combination of the solvent A to C is one of at least one ofn-hexane and n-heptane (solvent A), at least one of methanol and ethanol(solvent B), and at least one of acetone and 2-butaneone (solvent C).

<Radiation-Sensitive Resin Composition>

The radiation-sensitive resin composition of the present invention isused for forming a photoresist film in a process of forming a resistpattern, including a liquid immersion lithographic process in whichradiation is emitted through a liquid having a refractive index largerthan the refractive index of air at a wavelength of 193 nm, and beingpresent between a lens and the photoresist film, and is characterized inthat the radiation-sensitive resin composition for formation of thephotoresist film comprises the above-mentioned fluorine-containingpolymer (A), a resin (B) having an acid-unstable group, aradiation-sensitive acid generator (C), a nitrogen-containing compound(D) and a solvent (E).

In the present invention, the above-mentioned polymer (A) may be usedsingly or in combination of two or more thereof.

The polymer (A) may be used as an additive for a resist in the presentinvention. From the viewpoint of ensuring the resist film to secure asufficient receding contact angle and sufficiently suppressing elutionof acid generators from the resist film, the content of the polymer (A)is usually 0.1% or more by weight, preferably 0.1% to 40% by weight, andmore preferably 0.5% to 35% by weight based on 100% by weight of theradiation-sensitive resin composition of the present invention. If thecontent of the polymer (A) is less than 0.1% by weight, effects based onthe polymer (A) (high receding contact angle and low elution) are notexhibited, that is, the receding contact angle in the resist film may belowered or elution of an acid generator and the like from the resistfilm may not be suppressed. On the other hand, if the content is morethan 40% by weight, there is a possibility that the depth of focus of anisolated line may be small or a development defect may occur.

<Resin (B) Having Acid-Unstable Group>

The resin (B) having an acid-unstable group (hereinafter referred tosimply as “resin (B)”) according to the present invention is notparticularly limited because the radiation-sensitive resin compositionof the present invention exhibits effects based on the polymer (A) (highreceding contact angle and low elution), however, an alkali-insoluble orscarcely alkali-soluble resin is preferable which exhibitsalkali-solubility by the function of an acid. The term“alkali-insoluble” and “scarcely alkali-soluble” used herein indicatethe following properties: in the case of developing a film using onlythe resin (B) instead of a resist film formed using theradiation-sensitive resin composition containing the polymer (B) underalkaline development conditions employed for forming a resist pattern onthe resist film, 50% or more of the initial thickness of the resist filmremains after development.

Examples of the resin (B) include a resin having an alicyclic skeletonsuch as norbornane ring in the main chain obtained by polymerization ofa norbornene derivative and the like, a resin having a norbornane ringand a maleic anhydride derivative in the main chain obtained bycopolymerization of a norbornene derivative and maleic anhydride, aresin having a norbornane ring and a (meth)acrylic skeleton in the mainchain obtained by copolymerization of a norbornene derivative and a(meth)acrylic compound, a resin having a norbornane ring, a maleicanhydride derivative and a (meth)acrylic skeleton in the main chainobtained by copolymerization of a norbornene derivative, a maleicanhydride and a (meth)acrylic compound, a resin having a (meth)acrylicskeleton in the main chain obtained by copolymerization a (meth)acryliccompound, and the like. The term “(meth)acryl” means “acryl” or“methacryl”, or both.

Among the resins (B), a resin having the above-mentioned repeating unit(3) comprising a lactone skeleton is preferable. The same monomersmentioned above can be given as examples of preferable monomersproviding the repeating unit (3).

The resin (B) may comprise only one repeating unit (3) or two or moretypes thereof.

The content of the repeating unit (3) is preferably 5 mol % to 85 mol %,more preferably 10 mol % to 70 mol %, and further preferably 15 mol % to60 mol % based on 100 mol % of the total of the repeating units in thepolymer (B). If the content of the repeating unit (3) is less than 5 mol%, developability and exposure allowance tend to be impaired. If thecontent exceeds 85 mol %, solubility of the resin (B) in a solvent andresolution tend to be impaired.

Moreover, the resin (B) preferably comprises the repeating unit (2)represented by the above-mentioned general formula (2) in addition tothe repeating unit (3). A monomer providing the repeating unit (2) isthe same as one mentioned above and is particularly preferably a monomerhaving a monocyclic structure or a polycyclic structure.

The resin (B) may comprise only one repeating unit (2) or two or moretypes thereof.

The content of the repeating unit (2) is usually 10 mol % to 70 mol %,preferably 15 mol % to 60 mol %, and further preferably 20 mol % to 50mol % based on 100 mol % of the total of the repeating units in thepolymer (B). If the content of the repeating unit (2) is less than 10mol %, resolution in a resist may be decreased. If the content is morethan 70 mol %, developability and exposure allowance may be impaired.

The resin (B) according to the present invention may comprise one ormore of repeating unit other than the repeating units (2) and (3)(hereinafter referred to as “further repeating unit”).

The further repeating unit preferably contains at least one repeatingunit selected from the above-mentioned repeating unit (4) having analicyclic compound, the above-mentioned repeating unit (5) originatingfrom an aromatic compound, the following repeating unit represented bythe general formula (5) (hereinafter referred to as “repeating unit(6)”), and the following repeating unit represented by the generalformula (6) (hereinafter referred to as “repeating unit (7)”). The samemonomers mentioned above can be given as examples of preferable monomersproviding the repeating units (4) and (5).

[In the general formula (5), R⁹ represents hydrogen atom, an alkyl grouphaving 1 to 4 carbon atoms, a trifluoromethyl group or a hydroxymethylgroup, and R¹⁰ represents a divalent organic group.]

Examples of the alkyl group having 1 to 4 carbon atoms represented by R⁹in the general formula (5) include an alkyl group such as methyl group,ethyl group, n-propyl group, i-propyl group, n-butyl group,2-methylpropyl group, 1-methylpropyl group and t-butyl group.

In addition, the divalent organic group represented by R¹⁰ in thegeneral formula (5) is preferably a divalent hydrocarbon group. Amongthe divalent hydrocarbon group, a linear or cyclic hydrocarbon group ispreferable. And it may be an alkylene glycol group or an alkylene estergroup.

Preferable examples of R¹⁰ include a saturated chain hydrocarbon groupsuch as methylene group, ethylene group, propylene groups including1,3-propylene group and 1,2-propylene group, tetramethylene group,pentamethylene group, hexamethylene group, heptamethylene group,octamethylene group, nonamethylene group, decamethylene group,undecamethylene group, dodecamethylene group, tridecamethylene group,tetradecamethylene group, pentadecamethylene group, hexadecamethylenegroup, heptadecamethylene group, octadecamethylene group,nonadecamethylene group, icosylene group, 1-methyl-1,3-propylene group,2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group,1-methyl-1,4-butylene group, 2-methyl-1,4-butylene group, methylidenegroup, ethylidene group, propylidene group and 2-propylidene group; amonocyclic hydrocarbon group such as a cycloalkylene group having 3 to10 carbon atoms including cyclobutylene groups (e.g. 1,3-cyclobutylenegroup), cyclopentylene groups (e.g. 1,3-cyclopentylene group),cyclohexylene groups (e.g. 1,4-cyclohexylene group) and cyclooctylenegroups (e.g. 1,5-cyclooctylene group); a bridged cyclic hydrocarbongroup such as a cyclic hydrocarbon group with 2 to 4 rings having 4 to30 carbon atoms including norbornylene groups (e.g. 1,4-norbornylenegroup and 2,5-norbornylene group), and admantylene groups (e.g.1,5-admantylene group and 2,6-admantylene group); and the like.

In the case where R¹⁰ comprises a divalent alicyclic hydrocarbon groupin particular, it is preferable to insert an alkylene group having 1 to4 carbon atoms as a spacer between bis(trifluoromethyl)hydroxymethylgroup and the alicyclic hydrocarbon group.

Additionally, R¹⁰ is preferably a hydrocarbon group containing2,5-norbornylene group, 1,2-ethylene group and a propylene group.

As particularly preferable examples of the monomer which leads to therepeating unit (6),(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-3-propyl) (meth)acrylate,(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-butyl) (meth)acrylate,(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-5-pentyl) (meth)acrylate,(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl) (meth)acrylate,2-{[5-(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]bicyclo[2.2.1]heptyl}(meth)acrylate,3-{[8-(1′,1′,1′-trifluoro-2′-trifluoromethyl-2′-hydroxy)propyl]tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecyl}(meth)acrylate, and the like can be given.

[In the general formula (6), R¹¹ represents hydrogen atom or methylgroup, Y represents a single bond or a divalent organic group having 1to 3 carbon atoms, Z individually represents a single bond or a divalentorganic group having 1 to 3 carbon atoms, R¹² individually representshydrogen atom, a hydroxyl group, a cyano group, or a COOR¹³ group.]

Examples of the divalent organic group having 1 to 3 carbon atomsrepresented by Y and Z include methylene group, ethylene group andpropylene group.

Additionally, R¹³ in the COOR¹³ group represented by R¹² in the generalformula (6) represents hydrogen atom, a linear or branched alkyl grouphaving 1 to 4 carbon atoms, or an alicyclic alkyl group having 3 to 20carbon atoms. Examples of the linear or branched alkyl group having 1 to4 carbon atoms represented by R¹³ include methyl group, ethyl group,n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group,1-methylpropyl group, and t-butyl group.

Examples of the alicyclic alkyl group having 3 to 20 carbon atomsinclude a cycloalkyl group represented by —C_(n)H_(2n-1) (wherein n isan integer of 3 to 20) such as cyclopropyl group, cyclobutyl group,cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctylgroup. Further, a polyalicyclic alkyl group such as bicyclo[2.2.1]heptylgroup, tricyclo[5.2.1.0^(2,6)]decyl group,tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodecanyl group and adamantyl group; agroup in which a part of a cycloalkyl group or a polyalicyclic alkylgroup is substituted with one or more linear, branched or cyclic alkylgroup; and the like can be given.

When at least one of three R¹²s is not hydrogen atom and Y is a singlebond, at least one of three Zs is preferably a divalent organic grouphaving 1 to 3 carbon atoms.

Preferable examples of the monomer which leads to the repeating unit (7)include, 3-hydroxyadamantan-1-yl-methyl (meth)acrylate,3,5-dihydroxyadamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-cyanoadamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-carboxyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-methoxycarbonyladamantan-1-yl-methyl (meth)acrylate,3-hydroxymethyladamantan-1-yl-methyl (meth)acrylate,3,5-dihydroxymethyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-hydroxymethyladamantan-1-yl-methyl (meth)acrylate,3-cyano-5-hydroxymethyladamantan-1-yl-methyl (meth)acrylate,3-hydroxymethyl-5-carboxyladamantan-1-yl-methyl (meth)acrylate,3-hydroxymethyl-5-methoxycarbonyladamantan-1-yl-methyl (meth)acrylate,3-cyanoadamantane-1-yl-methyl (meth)acrylate,3,5-dicyanoadamantan-1-yl-methyl (meth)acrylate,3-cyano-5-carboxyladamantan-1-yl-methyl (meth)acrylate,3-cyano-5-methoxycarbonyladamantan-1-yl-methyl (meth)acrylate,3-carboxyladamantan-1-yl-methyl (meth)acrylate,3,5-dicarboxyladamantan-1-yl-methyl (meth)acrylate,3-carboxyl-5-methoxycarbonyladamantan-1-yl-methyl (meth)acrylate,3-methoxycarbonyladamantan-1-yl-methyl (meth)acrylate,3,5-dimethoxycarbonyladamantan-1-yl-methyl (meth)acrylate,

3-hydroxy-5-methyladamantan-1-yl (meth)acrylate,3,5-dihydroxy-7-methyladamantan-1-yl (meth)acrylate,3-hydroxy-5-cyano-7-methyladamantan-1-yl (meth)acrylate,3-hydroxy-5-carboxyl-7-methyladamantan-1-yl (meth)acrylate,3-hydroxy-5-methoxycarbonyl-7-methyladamantan-1-yl (meth)acrylate,3-hydroxymethyl-5-methyladamantan-1-yl (meth)acrylate,3,5-dihydroxymethyl-7-methyladamantan-1-yl (meth)acrylate,3-hydroxy-5-hydroxymethyl-7-methyladamantan-1-yl (meth)acrylate,3-cyano-5-hydroxymethyl-7-methyladamantan-1-yl (meth)acrylate,3-hydroxymethyl-5-carboxyl-7-methyladamantan-1-yl (meth)acrylate,3-hydroxymethyl-5-methoxycarbonyl-7-methyladamantan-1-yl (meth)acrylate,3-cyano-5-methyladamantan-1-yl (meth)acrylate,3,5-dicyano-7-methyladamantan-1-yl (meth)acrylate,3-cyano-5-carboxyl-7-methyladamantan-1-yl (meth)acrylate,3-cyano-5-methoxycarbonyl-7-methyladamantan-1-yl (meth)acrylate,3-carboxyl-5-methyladamantan-1-yl (meth)acrylate,3,5-dicarboxyl-7-methyladamantan-1-yl (meth)acrylate,3-carboxyl-5-methoxycarbonyl-7-methyladamantan-1-yl (meth)acrylate,3-methoxycarbonyl-5-methyladamantan-1-yl (meth)acrylate,3,5-dimethoxycarbonyl-7-methyladamantan-1-yl (meth)acrylate,

3-hydroxy-5-methyladamantan-1-yl-methyl (meth)acrylate,3,5-dihydroxy-7-methyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-cyano-7-methyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-carboxyl-7-methyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-methoxycarbonyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-hydroxymethyl-5-methyl adamantan-1-yl-methyl(meth)acrylate, 3,5-dihydroxymethyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-hydroxy-5-hydroxymethyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-cyano-5-hydroxymethyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-hydroxymethyl-5-carboxyl-7-methyladamantan-1-yl-methyl(meth)acrylate,3-hydroxymethyl-5-methoxycarbonyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-cyano-5-methyladamantan-1-yl-methyl (meth)acrylate,3,5-dicyano-7-methyladamantan-1-yl-methyl (meth)acrylate,3-cyano-5-carboxyl-7-methyladamantan-1-yl-methyl (meth)acrylate,3-cyano-5-methoxycarbonyl-7-methyladamantan-1-yl-methyl (meth)acrylate,3-carboxyl-5-methyladamantan-1-yl-methyl (meth)acrylate,3,5-dicarboxyl-7-methyladamantan-1-yl-methyl (meth)acrylate,3-carboxyl-5-methoxycarbonyl-7-methyladamantan-1-yl-methyl(meth)acrylate, 3-methoxycarbonyl-5-methyladamantan-1-yl-methyl(meth)acrylate, 3,5-dimethoxycarbonyl-7-methyladamantan-1-yl-methyl(meth)acrylate,

3-hydroxy-5,7-dimethyladamantan-1-yl (meth)acrylate,3-hydroxymethyl-5,7-dimethyladamantan-1-yl (meth)acrylate,3-cyano-5,7-dimethyladamantan-1-yl (meth)acrylate,3-carboxyl-5,7-dimethyladamantan-1-yl (meth)acrylate,3-methoxycarbonyl-5,7-dimethyladamantan-1-yl (meth)acrylate,3-hydroxy-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate,3-hydroxymethyl-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate,3-cyano-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate,3-carboxyl-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate,3-methoxycarbonyl-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate andthe like can be given.

Among these monomers, 3-hydroxyadamantan-1-yl-methyl (meth)acrylate,3,5-dihydroxyadamantan-1-yl-methyl (meth)acrylate,3-cyanoadamantan-1-yl-methyl (meth)acrylate,3-carboxyladamantan-1-yl-methyl (meth)acrylate,3-hydroxy-5-methyladamantan-1-yl-(meth)acrylate,3,5-dihydroxy-7-methyladamantan-1-yl (meth)acrylate,3-hydroxy-5,7-dimethyladamantan-1-yl (meth)acrylate,3-carboxyl-5,7-dimethyladamantan-1-yl (meth)acrylate,3-hydroxy-5,7-dimethyladamantan-1-yl-methyl (meth)acrylate and the likeare particularly preferred.

The resin (B) according to the present invention may further comprise arepeating unit (hereinafter referred to as “still other repeating unit”)in addition to the repeating units (4), (5), (6) and (7).

Examples of the still other repeating unit include units obtained bycleavage of a polymerizable unsaturated bond in a (meth)acrylate havinga bridged hydrocarbon skeleton such as dicyclopentenyl (meth)acrylateand adamantylmethyl (meth)acrylate; a carboxyl group-containing esterhaving a bridged hydrocarbon skeleton in an unsaturated carboxylic acidsuch as carboxylnorbornyl (meth)acrylate, carboxytricyclodecanyl(meth)acrylate and carboxytetracycloundecanyl (meth)acrylate;

a (meth)acrylate not having a bridged hydrocarbon skeleton such asmethyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate,n-butyl (meth)acrylate, 2-methylpropyl (meth)acrylate, 1-methylpropyl(meth)acrylate, t-butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,cyclopropyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl(meth)acrylate, 4-methoxycyclohexyl (meth)acrylate,2-cyclopentyloxycarbonylethyl (meth)acrylate,2-cyclohexyloxycarbonylethyl (meth)acrylate and2-(4-methoxycyclohexyl)oxycarbonylethyl (meth)acrylate;

an α-hydroxymethyl acrylate such as methyl α-hydroxymethyl acrylate,ethyl α-hydroxymethyl acrylate, n-propyl α-hydroxymethyl acrylate andn-butyl α-hydroxymethyl acrylate; an unsaturated nitrile compound suchas (meth)acrylonitrile, α-chloroacrylonitrile, crotonitrile,maleinitrile, fumaronitrile, mesaconitrile, citraconitrile anditaconitrile; an unsaturated amide compound such as (meth)acrylamide,N,N-dimethyl (meth)acrylamide, crotonamide, maleinamide, fumaramide,mesaconamide, citraconamide, and itaconamide; other nitrogen-containingvinyl compounds such as N-(meth)acryloylmorpholine,N-vinyl-ε-caprolactam, N-vinylpyrrolidone, vinylpyridine andvinylimidazole; an unsaturated carboxylic anhydride such as(meth)acrylic acid, crotonic acid, maleic acid, maleic anhydride,fumaric acid, itaconic acid, anhydrous itaconic acid, citraconic acid,anhydrous citraconic acid and mesaconic acid; a carboxylgroup-containing ester not having a bridged hydrocarbon skeleton in anunsaturated carboxylic acid such as 2-carboxyethyl (meth)acrylate,2-carboxypropyl (meth)acrylate, 3-carboxypropyl (meth)acrylate,4-carboxybutyl (meth)acrylate and 4-carboxycyclohexyl (meth)acrylate;

a polyfunctional monomer having a bridged hydrocarbon skeleton such as1,2-adamantanediol di(meth)acrylate, 1,3-adamantanedioldi(meth)acrylate, 1,4-adamantanediol di(meth)acrylate andtricyclodecanyl dimethylol di(meth)acrylate;

a polyfunctional monomer not having a bridged hydrocarbon skeleton suchas methylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate,propylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,2,5-dimethyl-2,5-hexanediol di(meth)acrylate, 1,8-octanedioldi(meth)acrylate, 1,9-nonanediol di(meth)acrylate,1,4-bis(2-hydroxypropyl)benzene di(meth)acrylate and1,3-bis(2-hydroxypropyl)benzene di(meth) acrylate; and the like.

Among these still other repeating units, the units obtained by cleavageof polymerizable unsaturated bond in a (meth)acrylate having a bridgedhydrocarbon skeleton and the like are preferable.

The acid-unstable group in the resin (B) according to the presentinvention preferably has a monocyclic structure or polycyclic structure.Specific examples of the structures include methyl cyclopentyl, ethylcyclopentyl, methyl cyclohexyl, ethyl cyclohexyl, methyl adamantyl,ethyl adamantyl and the like.

The resin (B) according to the present invention may comprise either onetype or two or more types of the repeating units selected from the groupconsisting of the repeating units (4), (5), (6) and (7) and the stillother repeating unit.

The content of the repeating unit (4) in the resin (B) is usually 30 mol% or less, and preferably 25 mol % or less based on 100 mol % of thetotal of the repeating units in the resin (B). If the content of therepeating unit (4) is more than 30 mol %, shape of a resist pattern maybe deteriorated or resolution may be impaired.

The content of the repeating unit (5) in the resin (B) is usually 40 mol% or less, and preferably 30 mol % or less based on 100 mol % of thetotal of the repeating units in the resin (B). If the content of therepeating unit (5) is more than 40 mol %, radiation transmission may bereduced and pattern profile may be deteriorated.

In addition, the content of the repeating unit (6) is usually 30 mol %or less, and preferably 25 mol % or less based on 100 mol % of the totalof the repeating units in the resin (B). If the content of the repeatingunit (6) is more than 30 mol %, a resultant resist film tends to swellin an alkali developer.

Further, the content of the repeating unit (7) is usually 30 mol % orless, and preferably 25 mol % or less based on 100 mol % of the total ofthe repeating units in the resin (B). If the content of the repeatingunit (7) is more than 30 mol %, a resultant resist film tends to swellin an alkali developer and solubility in an alkali developer may bedecreased.

Moreover, the content of the still other repeating unit is usually 50mol % or less, and preferably 40 mol % or less based on 100 mol % of thetotal of the repeating units in the resin (B).

The resin (B) according to the present invention can be produced bypolymerizing polymerizable unsaturated monomers corresponding to eachrepeating unit in the presence of a chain transfer agent as required,using a radical polymerization initiator such as a hydroperoxide, adialkyl peroxide, a diacyl peroxide, and an azo compound in anappropriate solvent.

Examples of the solvent used for polymerization include an alkane suchas n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane; acycloalkane such as cyclohexane, cycloheptane, cyclooctane, decalin andnorbornane; an aromatic hydrocarbon such as benzene, toluene, xylene,ethylbenzene and cumene; a halogenated hydrocarbon such aschlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromideand chlorobenzene; a saturated carboxylic acid ester such as ethylacetate, n-butyl acetate, i-butyl acetate and methyl propionate; aketone such as 2-butanone, 4-methyl-2-pentanone and 2-heptanone; anether such as tetrahydrofuran, dimethoxyethanes and diethoxyethanes; andthe like. These solvents may be used singly or in combination of two ormore thereof.

The polymerization temperature is usually in the range from 40° C. to150° C., and preferably from 50° C. to 120° C. The reaction time isusually in the range from 1 to 48 hours, and preferably from 1 to 24hours.

Although not particularly limited, the Mw of the resin (B) according tothe present invention determined by GPC is preferably in the range from1,000 to 100,000, more preferably 1,000 to 30,000, and still morepreferably 1,000 to 20,000. If the Mw of the resin (B) is 10,000 orless, heat resistance in a resist tends to be lowered. On the otherhand, if the Mw is more than 100,000, developability in a resist tendsto be decreased.

The ratio (Mw/Mn) of the Mw to the Mn determined by GPC of the resin (B)is normally in the range from 1 to 5, and preferably 1 to 3.

In the resin (B), the solids content of the low molecular weightcomponents originating from monomers used for preparing the resin (B) ispreferably 0.1% or less by weight, more preferably 0.07% or less byweight, and still more preferably 0.05% or less by weight based on 100%by weight of the resin. If the content is less than 0.1% by weight, theeluted amount in the liquid for liquid immersion lithography such aswater with which the resist film comes in contact during exposure can bereduced. In addition, it is possible to prevent generation of extraneoussubstances in the resist during storage, inhibit uneven resistapplication, and sufficiently suppress defects during pattern formation.

Examples of the above-mentioned low molecular weight componentsoriginating from the monomers include a monomer, a dimer, a trimer andan oligomer, and they may be ones having Mw of 500 or less. Thecomponent having Mw of 500 or less can be removed by the purificationmethod to be described. The amount of the low molecular weightcomponents can be determined by analysis of the resin using highperformance liquid chromatography (HPLC).

It is preferable that the resin (B) contain almost no impuritiescomprising halogens or metals. That can provide a resist leading toimproved sensitivity, resolution, process stability, pattern shape andthe like.

The resin (B) can be purified by a chemical purification method such aswashing with water and liquid-liquid extraction, a combination of thechemical purification method and a physical purification method such asultrafiltration and centrifugation, or the like.

In the present invention, the resin (B) may be used singly or incombination of two or more thereof.

<Radiation-Sensitive Acid Generator (C)>

The radiation-sensitive acid generator (C) according to the presentinvention (hereinafter referred to as “acid generator (C)”) is acompound which produces an acid by being exposed to light, causes anacid-dissociable group in the repeating unit (2) in the resin componentto dissociate (disconnect a protective group) by the function of theresultant acid to make the exposed part of the resist film readilysoluble in an alkaline developer, and form a positive-tone resistpattern.

The acid generator (C) is preferably one containing the followingcompound represented by the general formula (7) (hereinafter referred toas “acid generator 1”).

In the general formula (7), R¹⁴ represents hydrogen atom, fluorine atom,hydroxyl group, a linear or branched alkyl group having 1 to 10 carbonatoms, a linear or branched alkoxyl group having 1 to 10 carbon atoms,or a linear or branched alkoxycarbonyl group having 2 to 11 carbonatoms, R¹⁵ represents a linear or branched alkyl group having 1 to 10carbon atoms, an alkoxyl group, or a linear, branched or cyclicalkanesulfonyl group having 1 to 10 carbon atoms, R¹⁶ individuallyrepresents a linear or branched alkyl group having 1 to 10 carbon atoms,a phenyl group that may be substituted, or a naphthyl group that may besubstituted, or two R¹⁶s bond to form a divalent group which has 2 to 10carbon atoms and may be substituted, k is an integer of 0 to 2, X⁻represents the general formula R¹⁷C_(n)F_(2n)SO₃ ⁻ or R¹⁷SO₃ ⁻ (whereinR¹⁷ represents fluorine atom or a hydrocarbon group having 1 to 12carbon atoms, and n is an integer of 1 to 10), or the following anionrepresented by the general formula (8-1) or (8-2), and r is an integerof 0 to 10;

[In the formulas, R¹⁸ individually represents a linear or branched alkylgroup having fluorine atom and 1 to 10 carbon atoms, or two R¹⁸s incombination represent a divalent organic group having fluorine atom and2 to 10 carbon atoms, wherein the divalent organic group may have asubstituent.]

In the general formula (7), examples of the linear or branched alkylgroup having 1 to 10 carbon atoms represented by R¹⁴, R¹⁵ and R¹⁶include methyl group, ethyl group, n-propyl group, i-propyl group,n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butylgroup, n-pentyl group, neopentyl group, n-hexyl group, n-heptyl group,n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group and thelike. Among these alkyl groups, methyl group, ethyl group, n-butylgroup, t-butyl group and the like are preferable.

Examples of the linear or branched alkoxyl group having 1 to 10 carbonatoms represented by R¹⁴ and R¹⁵ include methoxy group, ethoxy group,n-propoxy group, i-propoxy group, n-butoxy group, 2-methylpropoxy group,I-methylpropoxy group, t-butoxy group, n-pentyloxy group, neopentyloxygroup, n-hexyloxy group, n-heptyloxy group, n-octyloxy group,2-ethylhexyloxy group, n-nonyloxy group, n-decyloxy group and the like.Among these, methoxy group, ethoxy group, n-propoxy group and n-butoxygroup are preferable.

Examples of the linear or branched alkoxycarbonyl group having 2 to 11carbon atoms represented by R¹⁴ include methoxycarbonyl group,ethoxycarbonyl group, n-propoxycarbonyl group, i-propoxycarbonyl group,n-butoxycarbonyl group, 2-methylpropoxycarbonyl group,1-methylpropoxycarbonyl group, t-butoxycarbonyl group,n-pentyloxycarbonyl group, neopentyloxycarbonyl group,n-hexyloxycarbonyl group, n-heptyloxycarbonyl group, n-octyloxycarbonylgroup, 2-ethylhexyloxycarbonyl group, n-nonyloxycarbonyl group,n-decyloxycarbonyl group and the like. Among these alkoxycarbonylgroups, methoxycarbonyl group, ethoxycarbonyl group, n-butoxycarbonylgroup and the like are preferable.

In addition, examples of the linear, branched or cyclic alkanesulfonylgroup having 1 to 10 carbon atoms represented by R¹⁵ includemethanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group,n-butanesulfonyl group, tert-butanesulfonyl group, n-pentanesulfonylgroup, neopentanesulfonyl group, n-hexanesulfonyl group,n-heptanesulfonyl group, n-octanesulfonyl group, 2-ethylhexanesulfonylgroup, n-nonanesulfonyl group, n-decanesulfonyl group,cyclopentanesulfonyl group, cyclohexanesulfonyl group and the like.Among these alkanesulfonyl groups, methanesulfonyl group, ethanesulfonylgroup, n-propanesulfonyl group, n-butanesulfonyl group,cyclopentansulfonyl group, cyclohexanesulfonyl group and the like arepreferable.

Further, r is preferably 0 to 2.

In the general formula (7), examples of the substituted or unsubstitutedphenyl group represented by R¹⁶ include phenyl group and a phenyl groupsubstituted with a linear, branched or cyclic alkyl group having 1 to 10carbon atoms including o-tolyl group, m-tolyl group, p-tolyl group,2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenylgroup, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group,3,5-dimethylphenyl group, 2,4,6-trimethylphenyl group, 4-ethylphenylgroup, 4-t-butylphenyl group, 4-cyclohexylphenyl group and4-fluorophenyl group; a group in which each of phenyl group andalkyl-substituted phenyl group is substituted with one or more groupsselected from the group consisting of hydroxyl group, carboxyl group,cyano group, nitro group, an alkoxyl group, an alkoxyalkyl group, analkoxycarbonyl group and an alkoxycarbonyloxy group; and the like.

Examples of the alkoxyl group as the substituent for the phenyl group oralkyl-substituted phenyl group include a linear, branched, or cyclicalkoxyl group having 1 to 20 carbon atoms such as methoxy group, ethoxygroup, n-propoxy group, i-propoxy group, n-butoxy group, 2-methylpropoxygroup, 1-methylpropoxy group, t-butoxy group, cyclopentyloxy group and acyclohexyloxy group; and the like.

Examples of the alkoxyalkyl group include a linear, branched or cyclicalkoxyalkyl group having 2 to 21 carbon atoms such as methoxymethylgroup, ethoxymethyl group, 1-methoxyethyl group, 2-methoxyethyl group,1-ethoxyethyl group and 2-ethoxyethyl group; and the like.

Examples of the alkoxycarbonyl group include a linear, branched orcyclic alkoxycarbonyl group having 2 to 21 carbon atoms such asmethoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group,i-propoxycarbonyl group, n-butoxycarbonyl group, 2-methylpropoxycarbonylgroup, 1-methylpropoxycarbonyl group, t-butoxycarbonyl group,cyclopentyloxycarbonyl group and cyclohexyloxycarbonyl group; and thelike.

Additionally, examples of the alkoxycarbonyloxy group include a linear,branched or cyclic alkoxycarbonyloxy group having 2 to 21 carbon atomssuch as methoxycarbonyloxy group, ethoxycarbonyloxy group,n-propoxycarbonyloxy group, i-propoxycarbonyloxy group,n-butoxycarbonyloxy group, t-butoxycarbonyloxy group,cyclopentyloxycarbonyl group and a cyclohexyloxycarbonyl group; and thelike.

Examples of the phenyl group that may be substituted as R¹⁵ in thegeneral formula (7) include phenyl group, 4-cyclohexylphenyl group,4-t-butylphenyl group, 4-methoxyphenyl group, 4-t-butoxyphenyl group andthe like.

Examples of the naphthyl group that may be substituted as R¹⁶ include anaphthyl group such as 1-naphthyl group, 2-methyl-1-naphthyl group,3-methyl-1-naphthyl group, 4-methyl-1-naphthyl group,5-methyl-1-naphthyl group, 6-methyl-1-naphthyl group,7-methyl-1-naphthyl group, 8-methyl-1-naphthyl group,2,3-dimethyl-1-naphthyl group, 2,4-dimethyl-1-naphthyl group,2,5-dimethyl-1-naphthyl group, 2,6-dimethyl-1-naphthyl group,2,7-dimethyl-1-naphthyl group, 2,8-dimethyl-1-naphthyl group,3,4-dimethyl-1-naphthyl group, 3,5-dimethyl-1-naphthyl group,3,6-dimethyl-1-naphthyl group, 3,7-dimethyl-1-naphthyl group,3,8-dimethyl-1-naphthyl group, 4,5-dimethyl-1-naphthyl group,5,8-dimethyl-1-naphthyl group, 4-ethyl-1-naphthyl group, 2-naphthylgroup, 1-methyl-2-naphthyl group, 3-methyl-2-naphthyl group and4-methyl-2-naphthyl group, and a substituted naphthyl group with alinear, branched or cyclic alkyl group having 1 to 10 carbon atoms; agroup in which each of naphthyl group and alkyl-substituted naphthylgroup is substituted with one or more groups selected from the groupconsisting of hydroxyl group, carboxyl group, cyano group, nitro group,an alkoxyl group, an alkoxyalkyl group, an alkoxycarbonyl group and analkoxycarbonyloxy group; and the like.

Examples of the alkoxyl group, alkoxyalkyl group, alkoxycarbonyl groupand alkoxycarbonyloxy group which are substituents include groupsexemplified for the above-mentioned phenyl group and alkyl-substitutedphenyl group.

The naphthyl group that may be substituted as R¹⁶ in the general formula(7) are preferably 1-naphthyl group, 1-(4-methoxynaphthyl) group,1-(4-ethoxynaphthyl) group, 1-(4-n-propoxynaphtyl) group,1-(4-n-butoxynaphthyl) group, 2-(7-methoxynaphtyl) group,2-(7-ethoxynaphtyl) group, 2-(7-n-propoxynaphtyl) group,2-(7-n-butoxynaphtyl) group and the like.

Preferable example of the divalent group having 2 to 10 carbon atomsformed by two R¹⁶s is a group capable of forming a 5 or 6 member ringtogether with the sulfur atom in the general formula (7), particularly a5 member ring (i.e. tetrahydrothiophene ring).

Additionally, examples of the substituent in the above divalent groupinclude a group such as hydroxyl group, carboxyl group, cyano group,nitro group, an alkoxyl group, an alkoxyalkyl group, an alkoxycarbonylgroup and an alkoxycarbonyloxy group that are exemplified for theabove-mentioned phenyl group and alkyl-substituted phenyl group, and thelike.

Preferable examples of R¹⁶ in the general formula (7) are methyl group,ethyl group, phenyl group, 4-methoxyphenyl group, 1-naphthyl group, anda divalent group having a tetrahydrothiophene cyclic structure in whichtwo R¹⁶s and sulfur atom are bonded, and the like.

X⁻ in the general formula (7) is an anion represented byR¹⁷C_(n)F_(2n)SO₃ ⁻, R¹⁷SO₃ ⁻, or the above formulas (8-1) or (8-2).When X⁻ is R¹⁷C_(n)F_(2n)SO₃ ⁻, —C_(n)F_(2n)— group is a perfluoroalkylgroup having carbon atoms of the number n. This group may be linear orbranched. And n is preferably 1, 2, 4 or 8.

The hydrocarbon group having 1 to 12 carbon atoms that may besubstituted as R¹⁷ is preferably an alkyl group having 1 to 12 carbonatoms, a cycloalkyl group or a bridge alicyclic hydrocarbon group.

Specific examples include methyl group, ethyl group, n-propyl group,i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropylgroup, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group,cyclohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group,n-nonyl group, n-decyl group, norbornyl group, norbornylmethyl group,hydroxynorbornyl group, adamantyl group and the like.

Additionally, R¹⁸ in the case where X⁻ is the above anion represented bythe general formula (8-1) or (8-2), individually may represents a linearor branched alkyl group having fluorine atom and 1 to 10 carbon atoms,or two R¹⁸s in combination may represent a divalent organic group havingfluorine atom and 2 to 10 carbon atoms, in this case, the divalentorganic group may have a substituent.

In the case where R¹⁸ in the general formula (8-1) or (8-2) is a linearor branched alkyl group having 1 to 10 carbon atoms, example thereofinclude trifluoromethyl group, pentafluoroethyl group,heptafuluoropropyl group, nonafluorobutyl group, dodecafluoropentylgroup, perfluorooctyl group and the like.

Additionally, in the case where R¹⁸ is a divalent organic group having 2to 10 carbon atoms, example thereof include tetrafluoroethylene group,hexafluoropropylene group, octafluorobutylene group, decafluoropentylenegroup, undecafluorohexylene group and the like.

Accordingly, preferable examples of the anion X⁻ in the general formula(7) include trifluoromethanesulfonate anion, perfluoro-n-butanesulfonateanion, perfluoro-n-octanesulfonate anion,2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate anion,2-bicyclo[2.2.1]hept-2-yl-1,1-difluoroethanesulfonate anion and anionsrepresented by the following formulas (9-1) to (9-7).

Specific examples of preferable compound represented by the generalformula (7) include triphenylsulfonium trifluoromethanesulfonate,tri-tert-butylphenylsulfonium trifluoromethanesulfonate,4-cyclohexylphenyl-diphenylsulfonium trifluoromethanesulfonate,4-methanesulfonylphenyl-diphenylsulfonium trifluoromethanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, 1-(4-n-butoxynaphthyl)tetrahydrothiopheniumtrifluoromethanesulfonate,

triphenylsulfonium perfluoro-n-butanesulfonate,tri-tert-butylphenylsulfonium perfluoro-n-butanesulfonate,4-cyclohexylphenyl-diphenylsulfonium perfluoro-n-butanesulfonate,4-methanesulfonylphenyl-diphenylsulfonium perfluoro-n-butanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumperfluoro-n-butanesulfonate, 1-(4-n-butoxynaphthyl)tetrahydrothiopheniumperfluoro-n-butanesulfonate,

triphenylsulfonium perfluoro-n-octanesulfonate,tri-tert-butylphenylsulfonium perfluoro-n-octanesulfonate,4-cyclohexylphenyl-diphenylsulfonium perfluoro-n-octanesulfonate,4-methanesulfonylphenyl-diphenylsulfonium perfluoro-n-octanesulfonate,1-(3,5-dimethyl 4-hydroxyphenyl)tetrahydrothiopheniumperfluoro-n-octanesulfonate, 1-(4-n-butoxynaphthyl)tetrahydrothiopheniumperfluoro-n-octanesulfonate,

triphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,tri-tert-butylphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,4-cyclohexylphenyl-diphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,4-methanesulfonylphenyldiphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,1-(4-n-butoxynaphthyl)tetrahydrothiophenium2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate,

triphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate,tri-tert-butylphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate,4-cyclohexylphenyldiphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate,4-methanesulfonylphenyl-diphenylsulfonium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate,1-(4-n-butoxynaphthyl)tetrahydrothiophenium2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate, compoundsrepresented by the following formulas B1 to B15, and the like.

In the present invention, the acid generator 1 may be used singly or incombination of two or more thereof.

Additionally, examples of the acid generator which can be used as theradiation-sensitive acid generator (C) other than the acid generator 1(hereinafter referred to as “other acid generator”) include an oniumsalt compound, a halogen-containing compound, a diazoketone compound, asulfone compound, a sulfonic acid compound and the like. Examples of theother acid generator are given below.

Onium Salt Compound:

Examples of the onium salt compound include an iodonium salt, asulfonium salt, a phosphonium salt, a diazonium salt, a pyridinium saltand the like.

Specific examples of the onium salt compound include diphenyliodoniumtrifluoromethanesulfonate, diphenyliodoniumnonafluoro-n-butanesulfonate, diphenyliodoniumperfluoro-n-octanesulfonate, diphenyliodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,bis(4-t-butylphenyl)iodonium trifluoromethanesulfonate,bis(4-t-butylphenyl)iodonium nonafluoro-n-butanesulfonate,bis(4-t-butylphenyl)iodonium perfluoro-n-octanesulfonate,bis(4-t-butylphenyl)iodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, cyclohexyl2-oxocyclohexyl methylsulfonium trifluoromethanesulfonate, dicyclohexyl2-oxocyclohexylsulfonium trifluoromethanesulfonate,2-oxocyclohexyldimethylsulfonium trifluoromethanesulfonate and the like.

Halogen-Containing Compound:

Examples of the halogen-containing compound include a haloalkylgroup-containing hydrocarbon compound, a haloalkyl group-containingheterocyclic compound and the like.

Specific examples of the halogen-containing compound include,(trichloromethyl)-s-triazine derivatives such asphenylbis(trichloromethyl)-s-triazine,4-methoxyphenylbis(trichloromethyl)-s-triazine and1-naphthylbis(trichloromethyl)-s-triazine;1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane and the like.

Diazoketone Compound:

Examples of the diazoketone compound include a 1,3-diketo-2-diazocompound, a diazobenzoquinone compound, a diazonaphthoquinone compoundand the like.

Specific examples of the diazoketone compound include1,2-naphthoquinonediazido-4-sulfonyl chloride,1,2-naphthoquinonediazido-5-sulfonyl chloride,1,2-naphthoquinonediazido-4-sulfonate or1,2-naphthoquinonediazido-5-sulfonate of2,3,4,4′-tetrahydroxybenzophenone, 1,2-naphthoquinonediazido-4-sulfonateor 1,2-naphthoquinonediazido-5-sulfonate of1,1,1-tris(4-hydroxyphenyl)ethane and the like.

Sulfone Compound:

Examples of the sulfone compound include a β-ketosulfone, aβ-sulfonylsulfone, an α-diazo compound of these compounds and the like.

Specific examples of the sulfone compound include 4-trisphenacylsulfone,mesitylphenacylsulfone, bis(phenylsulfonyl)methane and the like.

Sulfonic Acid Compound:

Examples of the sulfonic acid compound include an alkyl sulfonate, analkylimide sulfonate, a haloalkyl sulfonate, an aryl sulfonate, an iminosulfonate and the like.

Specific examples of the sulfone compound include benzoin tosylate,tris(trifluoromethanesulfonate) of pyrogallol,nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate,trifluoromethanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,nonafluoro-n-butanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,perfluoro-n-octanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,N-(trifluoromethanesulfonyloxy)succinimide,N-(nonafluoro-n-butanesulfonyloxy)succinimide,N-(perfluoro-n-octanesulfonyloxy)succinimide,N-(2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy)succinimide, 1,8-naphthalenedicarboxylic acid imidetrifluoromethanesulfonate, 1,8-naphthalenedicarboxylic acid imidenonafluoro-n-butanesulfonate, 1,8-naphthalenedicarboxylic acid imideperfluoro-n-octanesulfonate and the like.

Among these other acid generators, diphenyliodoniumtrifluoromethanesulfonate, diphenyliodoniumnonafluoro-n-butanesulfonate, diphenyliodoniumperfluoro-n-octanesulfonate, diphenyliodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,bis(4-t-butylphenyl)iodonium trifluoromethanesulfonate,bis(4-t-butylphenyl)iodonium nonafluoro-n-butanesulfonate,bis(4-t-butylphenyl)iodonium perfluoro-n-octanesulfonate,bis(4-t-butylphenyl)iodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, cyclohexyl2-oxocyclohexyl methylsulfonium trifluoromethanesulfonate, dicyclohexyl2-oxocyclohexylsulfonium trifluoromethanesulfonate,2-oxocyclohexyldimethylsulfonium trifluoromethanesulfonate,

trifluoromethanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,nonafluoro-n-butanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,perfluoro-n-octanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonylbicyclo[2.2.1]hept-5-ene-2,3-dicarbodiimide,N-(trifluoromethanesulfonyloxy)succinimide,N-(nonafluoro-n-butanesulfonyloxy)succinimide,N-(perfluoro-n-octanesulfonyloxy)succinimide,N-(2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy)succinimide,1,8-naphthalenedicarboxylic acid imide trifluoromethanesulfonate and thelike are preferable.

These other acid generators may be used singly or in combination of twoor more thereof.

Total amount of the acid generator 1 and other acid generator in thepresent invention is usually 0.1 to 20 parts by weight, and preferably0.5 to 10 parts by weight based on 100 parts by weight of the polymer(A) and the resin (B) in order to ensure a resist excellent insensitivity and developability. In this case if this total amount isless than 0.1 part by weight, sensitivity and developability tend to beimpaired. On the other hand, if the total amount is more than 20 partsby weight, transparency of a radiation tends to be decreased, whichmakes it difficult to obtain a rectangular resist pattern.

The proportion of the other acid generator to be added is 80% or less byweight, and preferably 60% or less by weight based on the total amountof the acid generator 1 and other acid generator.

<Nitrogen-Containing Compound (D)>

The nitrogen-containing compound (D) is a component which controlsdiffusion of an acid generated from the acid generator upon exposure inthe resist film and hinders undesired chemical reactions in theunexposed area. When the acid diffusion controller is added, storagestability of the resulting radiation-sensitive resin composition isimproved. In addition, resolution in a resist may be further improvedand changing of a resist pattern line width due to fluctuation ofpost-exposure delay (PED) from exposure to post-exposure heat treatmentcan be suppressed, whereby a composition with remarkably superiorprocess stability can be obtained.

Examples of the nitrogen-containing compound (D) include a tertiaryamine compound, other amine compounds, an amide group-containingcompound, a urea compound, a nitrogen-containing heterocyclic compoundand the like.

Preferable examples of the tertiary amine compound include amono(cyclo)alkylamine such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, n-decylamine and cyclohexylamine; a di(cyclo)alkylaminesuch as di-n-butylamine, di-n-pentylamine, di-n-hexylamine,di-n-heptylamine, di-n-octylamine, di-n-nonylamine, di-n-decylamine,cyclohexylmethylamine, and dicyclohexylamine; a tri(cyclo)alkylaminesuch as triethylamine, tri-n-propylamine, tri-n-butylamine,tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine,tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine,cyclohexyldimethylamine, methyldicyclohexylamine and tricyclohexylamine;a substituted alkylamine such as 2,2′,2″-nitrotriethanol; aniline,N-methylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-methylaniline, 4-nitroaniline, diphenylamine, triphenylamine,naphthylamine, 2,4,6-tri-tert-butyl-N-methylaniline,N-phenyldiethanolamine, 2,6-diisopropylaniline and the like.

Preferable examples of the above-mentioned other amine compound includeethylenediamine, N,N,N′,N′-tetramethylethylenediamine,tetramethylenediamine, hexamethylenediamine,4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether,4,4′-diaminobenzophenone, 4,4′-diaminodiphenylamine,2,2-bis(4-aminophenyl)propane,2-(3-aminophenyl)-2-(4-aminophenyl)propane,2-(4-aminophenyl)-2-(3-hydroxyphenyl)propane,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane,1,4-bis[1-(4-aminophenyl)-1-methylethyl]benzene,1,3-bis[1-(4-aminophenyl)-1-methylethyl]benzene,bis(2-dimethylaminoethyl) ether, bis(2-diethylaminoethyl) ether,1-(2-hydroxyethyl)-2-imidazolizinone, 2-quinoxalinol,N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine,N,N,N′,N″,N″-pentamethyldiethylenetriamine and the like.

Preferable examples of the preferable amide group-containing compoundinclude an N-t-butoxycarbonyl group-containing amino compound such asN-t-butoxycarbonyl di-n-octylamine, N-t-butoxycarbonyl di-n-nonylamine,N-t-butoxycarbonyl di-n-decylamine, N-t-butoxycarbonyldicyclohexylamine, N-t-butoxycarbonyl-1-adamantylamine,N-t-butoxycarbonyl-2-adamantylamine,N-t-butoxycarbonyl-N-methyl-1-adamantylamine,(S)-(−)-1-(t-butoxycarbonyl)-2-pyrrolidine methanol,(R)-(+)-1-(t-butoxycarbonyl)-2-pyrrolidine methanol,N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonylpyrrolidine,N-t-butoxycarbonylpiperazine, N-t-butoxycarbonylpiperidine,N,N-di-t-butoxycarbonyl-1-adamantylamine,N,N-di-t-butoxycarbonyl-N-methyl-1-adamantylamine,N-t-butoxycarbonyl-4,4′-diaminodiphenylmethane,N,N′-di-t-butoxycarbonylhexamethylenediamine,N,N,N′N′-tetra-t-butoxycarbonylhexamethylenediamine,N,N′-di-t-butoxycarbonyl-1,7-diaminoheptane,N,N′-di-t-butoxycarbonyl-1,8-diaminonooctane,N,N′-di-t-butoxycarbonyl-1,9-diaminononane,N,N′-di-t-butoxycarbonyl-1,10-diaminodecane,N,N′-di-t-butoxycarbonyl-1,12-diaminododecane,N,N′-di-t-butoxycarbonyl-4,4′-diaminodiphenylmethane,N-t-butoxycarbonylbenzimidazole,N-t-butoxycarbonyl-2-methylbenzimidazole andN-t-butoxycarbonyl-2-phenylbenzimidazole; formamide, N-methylformamide,N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone,N-methylpyrrolidone, N-acetyl-1-adamantylamine, tris(2-hydroxyethyl)isocyanurate and the like.

Preferable examples of the urea compound include urea, methylurea,1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea,1,3-diphenylurea, tri-n-butylthiourea and the like.

Preferable examples of the other nitrogen-containing heterocycliccompound include imidazoles such as imidazole, 4-methylimidazole,4-methyl-2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole,1-benzyl-2-methylimidazole and 1-benzyl-2-methyl-1H-imidazole; pyridinessuch as pyridine, 2-methylpyridine, 4-methylpyridine, 2-ethylpyridine,4-ethylpyridine, 2-phenylpyridine, 4-phenylpyridine,2-methyl-4-phenylpyridine, nicotine, nicotinic acid, nicotinamide,quinoline, 4-hydroxyquinoline, 8-oxyquinoline, acridine and2,2′:6′,2″-terpyridine; piperazines such as piperazine and1-(2-hydroxyethyl)piperazine; pyrazine, pyrazole, pyridazine,quinoxaline, purine, pyrrolidine, piperidine, piperidineethanol,3-piperidino-1,2-propanediol, morpholine, 4-methylmorpholine,1-(4-morpholinyl)ethanol, 4-acetylmorpholine,3-(N-morpholino)-1,2-propanediol, 1,4-dimethylpiperazine,1,4-diazabicyclo[2.2.2]octane and the like.

The above-mentioned nitrogen-containing compounds (D) may be used singlyor in combination of two or more thereof.

The amount of the acid diffusion controller (nitrogen-containingcompound (D)) to be added is usually 15 parts or less by weight,preferably 10 parts or less by weight, and more preferably 5 parts orless by weight based on 100 parts by weight of the total of the polymer(A) and the resin (B). If the amount of the acid diffusion controller tobe added exceeds 15 parts by weight, sensitivity in a resist tends to belowered. On the other hand, if the amount is less than 0.001 part byweight, the pattern shape or dimensional accuracy in a resist may bedecreased depending on the processing conditions.

<Solvent (E)>

The radiation-sensitive resin composition of the present invention isusually prepared in the form of a composition solution by dissolving thecomposition in a solvent so that the total solid content is usually inthe range from 1% to 50% by weight, and preferably 1% to 25% by weight,and filtering the solution with a filter having a pore diameter of about0.2 μm, for example.

Examples of the solvent (E) include a linear or branched ketone such as2-butanone, 2-pentanone, 3-methyl-2-butanone, 2-hexanone,4-methyl-2-pentanone, 3-methyl-2-pentanone, 3,3-dimethyl-2-butanone,2-heptanone and 2-octanone; a cyclic ketone such as cyclopentanone,3-methylcyclopentanone, cyclohexanone, 2-methylcyclohexanone,2,6-dimethylcyclohexanone and isophorone; a propylene glycol monoalkylether acetate such as propylene glycol monomethyl ether acetate,propylene glycol monoethyl ether acetate, propylene glycol mono-n-propylether acetate, propylene glycol mono-i-propyl ether acetate, propyleneglycol mono-n-butyl ether acetate, propylene glycol mono-i-butyl etheracetate, propylene glycol mono-sec-butyl ether acetate and propyleneglycol mono-t-butyl ether acetate; an alkyl 2-hydroxypropionate such asmethyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, n-propyl2-hydroxypropionate, i-propyl 2-hydroxypropionate, n-butyl2-hydroxypropionate, i-butyl 2-hydroxypropionate, sec-butyl2-hydroxypropionate and t-butyl 2-hydroxypropionate; an alkayl3-alkoxypropionate such as methyl 3-methoxypropionate, ethyl3-methoxypropionate, methyl 3-ethoxypropionate and ethyl3-ethoxypropionate; n-propyl alcohol, i-propyl alcohol, n-butyl alcohol,t-butyl alcohol, cyclohexanol, ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether,ethylene glycol mono-n-butyl ether, diethylene glycol dimethyl ether,diethylene glycol diethyl ether, diethylene glycol di-n-propyl ether,diethylene glycol di-n-butyl ether, ethylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, ethylene glycolmono-n-propyl ether acetate, propylene glycol monomethyl ether,propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether,toluene, xylene, ethyl 2-hydroxy-2-methylpropionate, ethylethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutyrate,3-methoxybutylacetate, 3-methyl-3-methoxybutylacetate,3-methyl-3-methoxybutylpropionate, 3-methyl-3-methoxybutylbutyrate,ethyl acetate, n-propyl acetate, n-butyl acetate, methyl acetoacetate,ethyl acetoacetate, methyl pyruvate, ethyl pyruvate, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, benzyl ethylether, di-n-hexyl ether, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, caproic acid, caprylic acid, 1-octanol,1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate, diethyloxalate, diethyl maleate, γ-butyrolactone, ethylene carbonate, propylenecarbonate and the like.

Among these, a linear or branched ketone, a cyclic ketone, a propyleneglycol monoalkyl ether acetate, an alkyl 2-hydroxypropionate, an alkyl3-alkoxypropionate, γ-butyrolactone and the like are preferable.

These solvents (E) may be used singly or in combination of two or morethereof.

<Additives>

The radiation-sensitive resin composition of the present inventionoptionally comprises various additives such as an aliphatic additive, asurfactant and a sensitizer.

The alicyclic additive is a component which further improves dry etchingtolerance, pattern shape, adhesion to substrate, and the like.

Examples of the alicyclic additive include an adamantane derivative suchas 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl1-adamantanecarboxylate, t-butoxycarbonylmethyl 1-adamantanecarboxylate,α-butyrolactone 1-adamantanecarboxylate, di-t-butyl1,3-adamantanedicarboxylate, t-butyl 1-adamantaneacetate,t-butoxycarbonylmethyl 1-adamantaneacetate, di-t-butyl1,3-adamantanediacetate and2,5-dimethyl-2,5-di(adamantylcarbonyloxy)hexane; a deoxycholate such ast-butyl deoxycholate, t-butoxycarbonylmethyl deoxycholate, 2-ethoxyethyldeoxycholate, 2-cyclohexyloxyethyl deoxycholate, 3-oxocyclohexyldeoxycholate, tetrahydropyranyl deoxycholate and mevalonolactonedeoxycholate; a lithocholate such as t-butyl lithocholate,t-butoxycarbonylmethyl lithocholate, 2-ethoxyethyl lithocholate,2-cyclohexyloxyethyl lithocholate, 3-oxocyclohexyl lithocholate,tetrahydropyranyl lithocholate and mevalonolactone lithocholate; analkyl carboxylate such as dimethyl adipate, diethyl adipate, dipropyladipate, di-n-butyl adipate and di-t-butyl adipate;3-[2-hydroxy-2,2-bis(trifluoromethyl)ethyl]tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecaneand the like. These alicyclic additives may be used singly or incombination of two or more thereof.

The surfactant is a component which improves applicability, striation,developability and the like.

Examples of the surfactant include a nonionic surfactant such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether,polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, andpolyethylene glycol distearate; commercially available products such as“KP341” (manufactured by Shin-Etsu Chemical Co., Ltd.), “Polyflow No.75” and “Polyflow No. 95” (manufactured by Kyoeisha Chemical Co., Ltd.),“EFTOP EF301”, “EFTOP EF303”, and “EFTOP EF352” (manufactured by JEMCO,Inc.), “MEGAFAC F171” and “MEGAFAC F173” (manufactured by Dainippon Inkand Chemicals, Inc.), “Fluorad FC430” and “Fluorad FC431” (manufacturedby Sumitomo 3M Ltd.), “Asahi Guard AG710”, “Surflon S-382”, “SurflonSC-101”, “Surflon SC-102”, “Surflon SC-103”, “Surflon SC-104”, “SurflonSC-105”, and “Surflon SC-106” (manufactured by Asahi Glass Co., Ltd.),and the like. These surfactants may be used singly or in combination oftwo or more thereof.

Additionally, the sensitizer is one that absorbs radiation energy andtransmits the energy to the acid generator (B), and exhibit the functionof the increasing the amount of an acid thereby. The sensitizer has animproving effect of apparent sensitivity of the radiation-sensitiveresin composition.

Examples of the sensitizer include carbazoles, acetophenones,benzophenones, naphthalenes, phenols, biacetyl, Eosine, Rose Bengal,pyrenes, anthracenes, phenothiazines and the like. These sensitizers maybe used singly or in combination of two or more thereof.

Further, when a dye or a pigment is formulated, a latent image in theexposed area can be visualized, thereby decreasing the effects ofhalation during exposure. Use of an adhesion aid improves adhesivity tothe substrate.

Examples of other additives include an alkali-soluble resin, a lowmolecular weight alkali solubility controller containing an aciddissociable protecting group, a halation inhibitor, a preservationstabilizer, an antifoaming agent and the like.

<Forming Method of Resist Pattern>

The radiation-sensitive resin composition of the present invention isparticularly useful for a chemically-amplified resist. In thechemically-amplified resist, an acid-dissociable group in the resincomponent, mainly resin (B) is dissociated by the function of an acidgenerated from the acid generator upon exposure, thereby producing acarboxyl group. As a result, solubility of the exposed part of theresist in an alkaline developer is increased, whereby the exposed partis dissolved in the alkaline developer and removed to obtain apositive-tone resist pattern.

In order to form a resist pattern using the radiation-sensitive resincomposition of the present invention, the resin composition solution iscoated to, for example, a substrate such as a silicon wafer and a wafercoated with aluminum using an appropriate application method includingrotational coating, cast coating, roll coating and the like. The resistfilm is then optionally pre-baked (hereinafter, referred to as “PB”) andexposed to radiation so as to form a prescribed resist pattern. Theradiation used for exposure is appropriately selected from visible rays,ultraviolet rays, deep ultraviolet rays, X-rays, charged particle beamsor the like depending on types of the acid generator. Among these, deepultraviolet rays represented by ArF excimer laser (wavelength: 193 nm)or KrF excimer laser (wavelength: 248 nm) are preferred. ArF excimerlaser (wavelength: 193 nm) is particularly preferable.

The exposure conditions such as exposure dose are appropriatelydetermined depending on the composition of the radiation-sensitive resincomposition, types of additives, and the like. In the present invention,it is preferable to perform post-exposure bake (PEB) after exposure. PEBensures smooth dissociation of the acid-dissociable group in the resincomponent. The heating temperature for PEB is usually in the range from30° C. to 200° C., and preferably 50° C. to 170° C., although theheating conditions are changed depending on the composition of theradiation-sensitive resin composition.

In order to bring out the potential of the radiation-sensitive resincomposition to the maximum extent, an organic or inorganicantireflection film may be formed on the substrate using a methoddescribed in, for example, JP-B H6-12452 (JP-A S59-93448) or the like. Aprotective film may be provided on the resist film in order to preventan adverse effect of basic impurities and the like that are present inthe environmental atmosphere using a method described in, for example,JP-A H5-188598 or the like. Moreover, in order to prevent the acidgenerator and the like from flowing out of the resist film during liquidimmersion lithography, a protective film for liquid immersionlithography may be provided on the resist film using a method describedin, for example, JP-A 2005-352384 or the like. These techniques may beused in combination.

The exposed resist film is then developed to form a prescribed resistpattern. The developer for development is preferably an alkaline aqueoussolution prepared by dissolving at least one of alkaline compounds suchas sodium hydroxide, potassium hydroxide, sodium carbonate, sodiumsilicate, sodium metasilicate, aqueous ammonia, ethylamine,n-propylamine, diethylamine, di-n-propylamine, triethylamine,methyldiethylamine, ethyldimethylamine, triethanolamine,tetramethylammonium hydroxide, pyrrole, piperidine, choline,1,8-diazabicyclo-[5.4.0]-7-undecene and1,5-diazabicyclo-[4.3.0]-5-nonene. The concentration of the alkalineaqueous solution is usually 10% or less by weight. If the concentrationof the alkaline aqueous solution exceeds 10% by weight, an unexposedpart may be dissolved in the developer and it is unfavorable.

The developer containing the alkaline aqueous solution may comprise anorganic solvent. Examples of the organic solvent include a ketone suchas acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone,cyclohexanone, 3-methylcyclopentanone and 2,6-dimethylcyclohexanone; analcohol such as methanol, ethanol, n-propanol, i-propanol, n-butanol,t-butanol, cyclopentanol, cyclohexanol, 1,4-hexanediol and1,4-hexanedimethylol; an ether such as tetrahydrofuran and dioxane; anester such as ethyl acetate, n-butyl acetate and i-amyl acetate; anaromatic hydrocarbon such as toluene and xylene; phenol,acetonylacetone, dimethylformamide; and the like. These organic solventsmay be used singly or in combination of two or more thereof. The amountof the organic solvent to be used is preferably 100% or less by volumeof the alkaline aqueous solution. The amount of the organic solventexceeding 100% by volume may decrease developability, giving rise to alarger undeveloped portion in the exposed area. In addition, anappropriate amount of a surfactant and the like may be added to thedeveloper containing the alkaline aqueous solution.

After development using the developer containing alkaline aqueoussolution, washing with water is generally carried out dried.

EXAMPLES

Embodiments of the present invention are described in detail hereinafterusing examples. The present invention is in no way limited by theseexamples. In addition, “part” is based on mass unless otherwiseindicated.

Measurement and evaluation in Synthesis Examples were carried outaccording to the methods as follows.

(1) Mw and Mn

These were measured by gel permeation chromatography (GPC) withmonodispersed polystyrene as a standard reference material using GPCcolumn (“G2000HXL”×2, “G3000HXL”×1, “G4000HXL”×1) manufactured by TosohCorp. under the following analysis conditions. Flow rate: 1.0 ml/min.,eluate: tetrahydrofuran, column temperature: 40° C. Dispersibility Mw/Mnwas calculated from the measurement result.

(2) ¹³C-NMR Analysis

¹³C-NMR analysis of the polymer was carried out using “JNM-EX270”manufactured by JEOL Ltd.

(3) Amount of Low Molecular Weight Components Originating from Monomers

The amount of low molecular components originating from monomers in 100%by weight of the polymer obtained in each Synthesis Example was measuredby high performance liquid chromatography (HPLC) using “Intersil ODS-25μm column” (4.6 mmφ×250 mm) manufactured by GL Sciences Inc., and aneluate of an acrylonitrile/0.1% phosphoric acid aqueous solution at aflow rate of 1.0 mL/min.

Hereinafter, Synthesis Example is described.

The monomers used for the synthesis of the fluorine-containing polymers(A) and the resins (B) are shown hereinunder by the formulas (M-1) to(M-12).

<Synthesis of Fluorine-Containing Polymers (A-1) to (A-13)>

Monomers and an initiator (MAIB; dimethyl-2,2′-azobis-iso-butyrate) wereused at amounts corresponding to mol % according to the formulationshown in Table 1 and dissolved in 50 g of methyl ethyl ketone to preparea monomer solution. The total amount of the monomers before startingpreparation was adjusted to 50 g. The mol % of each monomer indicatesmol % in the total amount of the monomers, and the mol % of eachinitiator indicates mol % in the total amount of the monomers and theinitiators.

On the other hand, 50 g of methyl ethyl ketone was charged into a 500-mLthree-necked flask equipped with a thermometer and a dropping funnel andnitrogen was purged for 30 minutes. After that, the content in the flaskwas heated to 80° C. while stirring using a magnetic stirrer.

Subsequently, the above monomer solution was added dropwise to the flaskusing a dropping funnel over three hours. After the addition, themixture was aged for three hours, and allowed to cool to a temperatureof 30° C. or lower, thereby obtaining a copolymer solution.

For post treatment, the fluorine-containing polymers (A-1) to (A-11)were purified by the following purification method (I) and thefluorine-containing polymers (A-12) and (A-13) were purified by thefollowing purification method (II).

Purification Method (I)

The reaction solution was added to a solvent for reprecipitation (referto Table 1) whose amount is five times of the amount of the reactionsolution, stirring was performed for 30 minutes, filtered, and thenrinsing was carried out twice in 200 mL of methanol. The resultantcopolymers were subjected to measurement for Mw, Mw/Mn (molecular weightdispersivity), yield (% by weight), content of low molecular weightcomponents (% by weight), and ratio of the repeating units in thecopolymers. The results are shown in Table 2.

Purification Method (II)

The reaction solution was transferred to a 2-L separatory funnel andthen homogeneously diluted with 150 g of n-hexane (solvent A), 600 g ofmethanol (solvent B) was added, and the mixture was stirred.Subsequently, 30 g of distilled water was charged, followed by stirringfor 30 minutes. The lower layer was collected to obtain a propyleneglycol monomethyl ether acetate solution. The resultant copolymers weresubjected to measurement for Mw, Mw/Mn, yield, content of low molecularweight components, and ratio of the repeating units in the copolymers.The results are shown in Table 2.

TABLE 1 Polymer Monomer Amount Monomer Amount Monomer Amount InitiatorSolvent for (A) 1 (mol %) 2 (mol %) 3 (mol %) (mol %) reprecipitationPolymerization Example 1 A-1 M-1 70 M-3 30 — 8 Methanol PolymerizationExample 2 A-2 M-2 70 M-3 30 — 8 Methanol/water = 4/1 PolymerizationExample 3 A-3 M-1 70 M-4 30 — 8 Methanol/water = 4/1 PolymerizationExample 4 A-4 M-1 70 M-5 30 — 8 Methanol/water = 4/1 PolymerizationExample 5 A-5 M-1 85 M-5 15 — 8 Methanol/water = 4/1 PolymerizationExample 6 A-6 M-1 30 M-5 70 — 8 Methanol/water = 4/1 PolymerizationExample 7 A-7 M-1 70 M-6 30 — 8 Methanol Polymerization Example 8 A-8M-1 85 M-5 15 — 12 Methanol Polymerization Example 9 A-9 M-1 70 M-5 15M-7 15 8 Methanol Polymerization Example 10 A-10 M-1 80 M-5 15 M-7 5 8Methanol Polymerization Example 11 A-11 M-1 70 M-10 30 — 8Methanol/water = 4/1 Polymerization Example 12 A-12 M-1 70 M-10 30 — 8 —Polymerization Example 13 A-13 M-1 85 M-5 15 — 12 —

TABLE 2 Low molecular Polymer Yield weight component Monomer 1 Monomer 2Monomer 3 (A) (%) (%) Mw Mw/Mn (mol %) (mol %) (mol %) PolymerizationExample 1 A-1 64 <0.1 6,600 1.51 67.4 32.6 — Polymerization Example 2A-2 29 <0.1 9,100 1.77 57.4 42.6 — Polymerization Example 3 A-3 86 <0.18,200 1.87 68.8 31.2 — Polymerization Example 4 A-4 82 <0.1 5,900 1.8771.6 28.4 — Polymerization Example 5 A-5 79 <0.1 5,200 1.82 85.5 14.5 —Polymerization Example 6 A-6 68 <0.1 6,400 1.63 33.2 66.8 —Polymerization Example 7 A-7 50 <0.1 7,200 2.00 71.1 28.9 —Polymerization Example 8 A-8 45 <0.1 4,000 1.80 85.3 14.7 —Polymerization Example 9 A-9 78 <0.1 8,000 1.63 70.1 14.1 15.8Polymerization Example 10 A-10 75 <0.1 6,800 1.65 79.1 15.6  5.3Polymerization Example 11 A-11 66 <0.1 7,000 1.60 70.5 29.5 —Polymerization Example 12 A-12 60 <0.1 7,200 2.00 71.1 28.9 —Polymerization Example 13 A-13 60 <0.1 4,000 1.80 85.3 14.7 —

The results of ¹³C-NMR analysis of A-1 to A-13 were as follows.

A-1: Peak originating from monomer (M-1) is at 95 ppm and has an area of2.067, peak originating from monomer (M-3) is at 85 to 90 ppm and has anarea of 1.000, and M-1/M-3=67.4/32.6 (mol %)

A-2: Peak originating from monomer (M-2) at 95 ppm: 1.650, peakoriginating from monomer (M-3) at 85 to 90 ppm: 1.225, andM-2/M-3=57.4/42.6 (mol %)

A-3: Peak originating from monomer (M-1) at 95 ppm: 2.834, peakoriginating from monomer (M-4) at 85 to 90 ppm: 1.286, andM-1/M-4=68.8/31.2 (mol %)

A-4: Peak originating from monomer (M-1) at 95 ppm is 2.672, peaksoriginating from monomer (M-5) at 110 to 120 ppm and at 60 to 70 ppm arerespectively 1.000 and 1.117, and M-1/M-5=71.6/28.4 (mol %)

A-5: Peak originating from monomer (M-1) at 95 ppm is 5.899, peakoriginating from monomer (M-5) at 110 to 120 ppm is 1.000, andM-1/M-5=85.5/14.5 (mol %)

A-6: Peak originating from monomer (M-1) at 95 ppm is 1.012, peaksoriginating from monomer (M-5) at 110 to 120 ppm and at 60 to 70 ppm arerespectively 1.946 and 2.130, and M-1/M-5=33.2/66.8 (mol %)

A-7: Peak originating from monomer (M-1) at 95 ppm is 2.487, peaksoriginating from monomer (M-6) at 100 to 130 ppm and at 60 ppm arerespectively 2.045 and 1.000, and M-1/M-6=71.1/28.9 (mol %)

A-8: Peak originating from monomer (M-1) at 95 ppm is 6.600, peakoriginating from monomer (M-5) at 60 to 70 ppm is 1.139, andM-1/M-5=85.3/14.7 (mol %)

A-9: Peak originating from monomer (M-1) at 95 ppm is 4.989, a peakoriginating from monomer (M-5) at 110 to 120 ppm is 1.000, peakoriginating from monomer (M-7) is 1.124, and M-1/M-5/M-7=70.1/14.1/15.8(mol %)

A-10: Peak originating from monomer (M-1) at 95 ppm is 15.905, a peakoriginating from monomer (M-5) at 110 to 120 ppm is 2.961, peakoriginating from monomer (M-7) at 85 ppm is 1.000, andM-1/M-5/M-7=79.1/15.6/5.3 (mol %)

A-11: Peak originating from monomer (M-1) at 95 ppm is 5.343, peakoriginating from monomer (M-10) at 60 ppm is 2.300, andM-1/M-10=70.5/29.5 (mol %)

A-12: Peak originating from monomer (M-1) at 95 ppm is 5.343, peakoriginating from monomer (M-10) at 60 ppm is 2.300, andM-1/M-10=70.5/29.5 (mol %)

A-13: Peak originating from monomer (M-1) at 95 ppm is 6.600, peakoriginating from monomer (M-5) at 60 to 70 ppm is 1.139, andM-1/M-5=85.3/14.7 (mol %)

<Synthesis of Resin (B-1)>

A monomer solution was prepared by dissolving 53.93 g (50 mol %) of themonomer (M-7), 35.38 g (40 mol %) of the monomer (M-1), and 10.69 g (10mol %) of the monomer (M-8) in 200 g of 2-butanone, and further adding5.58 g of dimethyl 2,2′-azobis(2-methylpropionate). On the other hand,100 g of 2-butanone was charged into a 500-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (74 g, yield 74%).

The polymer was a copolymer having Mw of 6,900, Mw/Mn=1.70 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-1) and the monomer (M-8) determined by ¹³C-NMR analysis of53.0:37.2:9.8 (mol %). This polymer is indicated as resin (B-1). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-1) was 0.03% by weight based on 100% by weight of thepolymer.

<Synthesis of Resin (B-2)>

A monomer solution was prepared by dissolving 55.44 g (50 mol %) of themonomer (M-7), 33.57 g (40 mol %) of the monomer (M-9), and 10.99 g (10mol %) of the monomer (M-8) in 200 g of 2-butanone, and further adding5.74 g of dimethyl 2,2′-azobis(2-methylpropionate). On the other hand,100 g of 2-butanone was charged into a 500-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (72 g, yield 72%).

The polymer was a copolymer having Mw of 9,100, Mw/Mn=1.56 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-9) and the monomer (M-8) determined by ¹³C-NMR analysis of52.2:38.1:9.7 (mol %). This polymer is indicated as resin (B-2). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-2) was 0.02% by weight based on 100% by weight of thepolymer.

<Synthesis of Resin (B-3)>

A monomer solution was prepared by dissolving 41.32 g (41 mol %) of themonomer (M-7), 44.63 g (42 mol %) of the monomer (M-11), and 14.05 g (17mol %) of the monomer (M-12) in 200 g of 2-butanone, and further adding5.74 g of dimethyl 2,2′-azobis(2-methylpropionate). On the other hand,100 g of 2-butanone was charged into a 500-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (72 g, yield 72%).

The polymer was a copolymer having Mw of 5,900, Mw/Mn=1.60 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-11) and the monomer (M-12) determined by ¹³C-NMR analysis of41.1:42.3:16.6 (mol %). This polymer is indicated as resin (B-3). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-3) was 0.1% or less by weight based on 100% by weight ofthe polymer.

<Synthesis of Resin (B-4)>

A monomer solution was prepared by dissolving 39.36 g (40 mol %) of themonomer (M-7), 5.65 g (7 mol %) of the monomer (M-1), and 54.99 g (53mol %) of the monomer (M-11) in 200 g of 2-butanone, and further adding6.54 g of dimethyl 2,2′-azobis(isobutylonitrile). On the other hand, 100g of 2-butanone was charged into a 500-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (75 g, yield 75%).

The polymer was a copolymer having Mw of 3,700, Mw/Mn=1.40 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-1) and the monomer (M-11) determined by ¹³C-NMR analysis of41.1:6.9:52.0 (mol %). This polymer is indicated as resin (B-4). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-4) was 0.1% or less by weight based on 100% by weight ofthe polymer.

<Synthesis of Resin (B-5)>

A monomer solution was prepared by dissolving 47.19 g (47 mol %) of themonomer (M-7), 11.53 g (14 mol %) of the monomer (M-1), and 41.29 g (39mol %) of the monomer (M-11) in 200 g of 2-butanone, and further adding4.08 g of dimethyl 2,2′-azobis(isobutylonitrile). On the other hand, 100g of 2-butanone was charged into a 1,000-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (75 g, yield 75%).

The polymer was a copolymer having Mw of 5,900, Mw/Mn=1.50 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-1) and the monomer (M-11) determined by ¹³C-NMR analysis of46.2:14.6:39.2 (mol %). This polymer is indicated as resin (B-5). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-5) was 0.1% or less by weight based on 100% by weight ofthe polymer.

<Synthesis of Resin (B-6)>

A monomer solution was prepared by dissolving 38.74 g (40 mol %) of themonomer (M-7) and 61.26 g (60 mol %) of the monomer (M-11) in 200 g of2-butanone, and further adding 4.08 g of dimethyl2,2′-azobis(isobutylonitrile). On the other hand, 100 g of 2-butanonewas charged into a 1,000-mL three-necked flask and nitrogen was purgedfor 30 minutes. After purging nitrogen to the flask, the content washeated to 80° C. while stirring and the above monomer solution was addeddropwise using a dropping funnel over three hours. The initiation of theaddition was set to a polymerization starting time and polymerizationwas carried out for six hours. After the polymerization, the polymersolution was cooled with water to a temperature of 30° C. or lower andwas poured into 2,000 g of methanol. A white precipitate produced wascollected by filtration. The white powder collected by filtration waswashed twice with 400 g of methanol in a slurry state, filtered again,and dried at 50° C. for 17 hours to obtain a polymer in the form ofwhite powder (73 g, yield 73%).

The polymer was a copolymer having Mw of 5,200, Mw/Mn=1.67 and mol %ratio of the repeating units originating from the monomer (M-11) and themonomer (M-7) determined by ¹³C-NMR analysis of 59.5:40.5 (mol %). Thispolymer is indicated as resin (B-6). The content of low-molecular weightcompounds originating from the monomers in the resin (B-6) was 0.1% orless by weight based on 100% by weight of the polymer.

<Synthesis of Resin (B-7)>

A monomer solution was prepared by dissolving 31.30 g (30 mol %) of themonomer (M-7), 29.09 g (34 mol %) of the monomer (M-1), and 39.61 g (36mol %) of the monomer (M-11) in 200 g of 2-butanone, and further adding4.08 g of dimethyl 2,2′-azobis(isobutylonitrile). On the other hand, 100g of 2-butanone was charged into a 1,000-mL three-necked flask andnitrogen was purged for 30 minutes. After purging nitrogen to the flask,the content was heated to 80° C. while stirring and the above monomersolution was added dropwise using a dropping funnel over three hours.The initiation of the addition was set to a polymerization starting timeand polymerization was carried out for six hours. After thepolymerization, the polymer solution was cooled with water to atemperature of 30° C. or lower and was poured into 2,000 g of methanol.A white precipitate produced was collected by filtration. The whitepowder collected by filtration was washed twice with 400 g of methanolin a slurry state, filtered again, and dried at 50° C. for 17 hours toobtain a polymer in the form of white powder (72 g, yield 72%).

The polymer was a copolymer having Mw of 5,000, Mw/Mn=1.65 and mol %ratio of the repeating units originating from the monomer (M-7), themonomer (M-1) and the monomer (M-11) determined by ¹³C-NMR analysis of30.4:33.8:35.8 (mol %). This polymer is indicated as resin (B-7). Thecontent of low-molecular weight compounds originating from the monomersin the resin (B-7) was 0.1% or less by weight based on 100% by weight ofthe polymer.

<Preparation of Radiation-Sensitive Resin Compositions>

The radiation-sensitive resin compositions for Examples 1 to 34 andComparative Examples 1 and 2 were prepared by mixing thefluorine-containing polymer (A), resin (B), acid generator (C),nitrogen-containing compound (D) and solvent (E) according toproportions shown in Tables 3 to 5.

TABLE 3 Nitrogen- Acid containing Polymer Resin generator compoundSolvent (A) (B) (C) (D) (E) (part) (part) (part) (part) (part) Example 1A-1 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2 (30)Example 2 A-2 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2(30) Example 3 A-3 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2(6.0) E-2 (30) Example 4 A-4 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1(1400) C-2 (6.0) E-2 (30) Example 5 A-5 (5) B-1 (95) C-1 (1.5) D-1(0.65) E-1 (1400) C-2 (6.0) E-2 (30) Example 6 A-6 (5) B-1 (95) C-1(1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2 (30) Example 7 A-7 (5) B-1(95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2 (30) Example 8 A-8(5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2 (30) Example9 A-9 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0) E-2 (30)Example 10 A-5 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (1400) C-2 (6.0)E-2 (30) Example 11 A-5 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1 (980) C-2(6.0) E-4 (420) Example 12 A-5 (5) B-1 (95) C-1 (1.5) D-1 (0.65) E-1(980) C-2 (6.0) E-3 (420) Example 13 A-10 (5) B-1 (95) C-1 (1.5) D-1(0.65) E-1 (1400) C-2 (6.0) E-2 (30)

TABLE 4 Nitrogen- Acid containing Polymer Resin generator compoundSolvent (A) (B) (C) (D) (E) (part) (part) (part) (part) (part) Example14 A-8 (5) B-2 (95) C-4 (6.5) D-1 (1.10) E-1 (1400) C-5 (2.0) E-2 (30)E-4 (600) Example 15 A-11 (5) B-2 (95) C-4 (6.5) D-1 (1.10) E-1 (1400)C-5 (2.0) E-2 (30) E-4 (600) Example 16 A-12 (5) B-3 (85) C-1 (4.0) D-1(1.10) E-1 (1400) B-5 (15) C-2 (4.0) E-2 (30) E-4 (600) Example 17 A-12(5) B-3 (85) C-1 (2.0) D-1 (1.10) E-1 (1400) B-5 (15) C-2 (6.0) E-2 (30)E-4 (600) Example 18 A-12 (5) B-3 (30) C-1 (4.0) D-1 (1.10) E-1 (1400)B-5 (70) C-2 (5.0) E-2 (30) E-4 (600) Example 19 A-12 (5) B-3 (30) C-6(4.0) D-1 (1.10) E-1 (1400) B-5 (70) C-2 (5.0) E-2 (30) E-4 (600)Example 20 A-12 (5) B-5 (100) C-1 (7.0) D-1 (1.10) E-1 (1400) C-2 (2.0)E-2 (30) E-4 (600) Example 21 A-12 (5) B-3 (30) C-1 (4.0) D-1 (1.10) E-1(1400) B-4 (70) C-2 (5.0) E-2 (30) E-4 (600) Example 22 A-12 (5) B-3(40) C-6 (4.0) D-1 (1.10) E-1 (1400) B-6 (60) C-2 (5.0) E-2 (30) E-4(600) Example 23 A-12 (5) B-3 (30) C-1 (7.0) D-1 (1.10) E-1 (1400) B-4(70) C-2 (2.0) E-2 (30) E-4 (600) Example 24 A-12 (5) B-3 (30) C-1 (7.0)D-1 (1.10) E-1 (1400) B-4 (70) C-5 (2.0) E-2 (30) E-4 (600) Example 25A-13 (5) B-5 (100) C-1 (7.0) D-1 (1.10) E-1 (140) C-2 (2.0) E-2 (30) E-4(600)

TABLE 5 Nitrogen- Acid containing Polymer Resin generator compoundSolvent (A) (B) (C) (D) (E) (part) (part) (part) (part) (part) Example26 A-12 (5) B-5 (100) C-1 (3.0) D-1 (1.10) E-1 (1400) C-2 (2.0) E-2 (30)C-6 (4.5) E-4 (600) Example 27 A-12 (5) B-5 (100) C-1 (7.0) D-1 (1.10)E-1 (1400) C-2 (2.0) E-2 (30) E-4 (600) Example 28 A-12 (5) B-6 (100)C-7 (2.0) D-1 (1.10) E-1 (1400) C-2 (4.0) E-2 (30) C-5 (2.0) E-4 (600)Example 29 A-12 (5) B-6 (100) C-7 (2.0) D-1 (1.10) E-1 (1400) C-2 (6.0)E-2 (30) E-4 (600) Example 30 A-12 (5) B-6 (100) C-7 (4.0) D-1 (1.10)E-1 (1400) C-1 (3.0) E-2 (30) E-4 (600) Example 31 A-13 (5) B-1 (100)C-1 (1.5) D-1 (1.10) E-1 (1400) C-2 (6.0) E-2 (30) E-4 (600) Example 32A-12 (5) B-1 (100) C-1 (1.5) D-1 (1.10) E-1 (1400) C-2 (6.0) E-2 (30)E-4 (600) Example 33 A-12 (5) B-7 (100) C-7 (7.5) D-1 (1.10) E-1 (1400)E-2 (30) E-4 (600) Example 34 A-12 (5) B-7 (100) C-6 (7.0) D-1 (1.10)E-1 (1400) E-2 (30) E-4 (600) Comparative — B-1 (100) C-1 (1.5) D-1(0.65) E-1 (1400) Example 1 C-2 (6.0) E-2 (30) Comparative — B-2 (100)C-4 (6.5) D-1 (1.10) E-1 (1400) Example 2 C-5 (2.0) E-2 (30) E-4 (600)

Details of the acid generator (C), nitrogen-containing compound (D) andsolvent (E) shown in Tables 3 to 5 are as follows. In the Tables, “part”is based on weight unless otherwise indicated.

<Acid Generator (C)>

-   (C-1): Triphenylsulfonium nonafluoro-n-butanesulfonate-   (C-2): 1-(4-n-butoxynaphthyl)tetrahydrothiophenium    perfluoro-n-butanesulfonate-   (C-3) Compound represented by the following formula

-   (C-4): Triphenylsulfonium    2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate-   (C-5): 1-(4-n-butoxynaphthyl)tetrahydrothiophenium    2-(bicyclo[2.2.1]hept-2′-yl)-1,1,2,2-tetrafluoroethanesulfonate-   (C-6): 4-cyclohexylphenyldiphenylsulfonium    nonafluoro-n-butanesulfonate-   (C-7): Triphenylsulfonium    2-(bicyclo[2.2.1]hept-2′-yl)-1,1-difluoroethanesulfonate    <Nitrogen-Containing Compound (D)>-   (D-1): N-t-butoxycarbonyl-4-hydroxypiperidine    <Solvent (E)>    (E-1): Propylene glycol monomethyl ether acetate    (E-2): γ-butyrolactone    (E-3): Ethyl lactate    (E-4): Cyclohexanone    <Evaluation of Radiation-Sensitive Resin Compositions>

The radiation-sensitive compositions according to Examples 1 to 13 andExamples 21 to 34 and Comparative Example 1 were subjected to evaluation(1) to (4) indicated below. Results of the evaluations are shown inTables 6 and 7.

In addition, the radiation-sensitive compositions according to Examples14 and 15, and Comparative Example 2 were subjected to evaluation (1),(2) and (5) to (8) below. Results of the evaluations are shown in Table8.

Further, the radiation-sensitive compositions according to Examples 16to 20 were subjected to evaluation (1), (2) and (9) to (12) below.Results of the evaluations are shown in Table 9.

The evaluation methods were as follows.

(1) Measurement of Eluted Amount

A 30 cm×30 cm square silicone rubber sheet 4 with a thickness of 1.0 mm(manufactured by Kureha Elastomer Co., Ltd.), of which the center wascut out in the form of a disk with a diameter of 11.3 cm was superposedon the center of an 8-inch silicon wafer 3 which was previously treatedwith HMDS (hexamethyldisilazane) 31 at 100° C. for 60 seconds using“CLEAN TRACK ACT 8” (manufactured by Tokyo Electron, Ltd.), as shown inFIG. 1. Subsequently, the cutout area at the center of the siliconerubber sheet was filled with 10 mL of ultra pure water 5 using a 10-mLtransfer pipette.

After that, a silicon wafer 6 having an underlayer antireflection film61 with a thicknesses of 77 nm (“ARC29A” manufactured by Bruwer Science)formed using “CLEAN TRACK ACT 8”, and a resist film 62 with athicknesses of 205 nm formed by applying resist compositions shown inTables 3 and 5 on the underlayer antireflection film 61 by spin coatingusing “CLEAN TRACK ACT 8” and baking at 115° C. for 60 seconds, wassuperposed on the above-mentioned silicone rubber sheet 14 in a mannersuch that the resist coating surface comes in contact with theabove-mentioned ultra pure water 5, and the ultra pure water 5 does notleak from the silicon rubber sheet 4.

10 seconds were holded as it is, and then the above-mentioned 8-inchsilicon wafer 6 was removed and the ultra pure water 5 was collectedusing a glass pipette for use as a sample for analysis. The recoveryrate of the ultra pure water after the experiment was 95% or more.

Next, the collected ultra pure water was subjected to a measurement ofLC-MS using a liquid chromatograph mass spectrometer having “SERIES1100” manufactured by AGILENT Corp. for LC section, and “Mariner”manufactured by Perseptive Biosystems, Inc. for MS section under thefollowing conditions to obtain the peak intensity of an anion part ofthe acid generator. In this instance, peak intensities of the aqueoussolutions containing the radiation-sensitive acid generator atconcentrations of 1 ppb, 10 ppb, and 100 ppb were measured under theabove conditions to prepare a calibration curve. The eluted amount wascalculated from the above peak intensity using this calibration curve.In the same manner, the peak intensities of aqueous solutions of theacid diffusion controller at concentrations of 1 ppb, 10 ppb, and 100ppb were measured under the same conditions to prepare a calibrationcurve. The eluted amount of the acid diffusion controller was calculatedfrom the above peak intensity using this calibration curve. Theevaluation criteria were as “Good” when the eluted amount was 5.0×10⁻¹²mol/cm²/sec or more, and as “Bad” when the amount was less than that.

(Column Conditions)

Column: One column of “CAPCELL PAK MG” manufactured by Shiseido Co.,Ltd.

Flow rate: 0.2 mL/min.

Eluate: A 3:7 mixture of water and methanol, with 0.1% by weight offormic acid added

Measurement temperature: 35° C.

(2) Measurement of Receding Contact Angle

After fabricating a substrate (wafer) wherein a film was formed with theradiation-sensitive resin composition using “DSA-10” manufactured byKRUS, it was promptly measured at room temperature (23° C.) and humidityof 45% under atmospheric pressure according to the following procedure.

<1> Adjust the wafer stage position,

<2> set the wafer on a stage,

<3> charge water to a needle,

<4> minutely adjust the needle position,

<5> inject water from the needle onto the wafer to form a 25-μLwaterdrop,

<6> withdraw the needle from the waterdrop,

<7> replace the needle again to the position adjusted in <4>,

<8> suck up water from the needle for 90 seconds at a rate of 10 μL/minand, at the same time, measure the contact angle once every second(total of 90 times), and

<9> starting from the time when the measured contact angle values arestabilized, the contact angles at 20 points are measured and averaged toobtain the receding contact angle.

(3) Sensitivity (i)

A 12-inch silicon wafer on which an underlayer antireflection film witha thickness of 77 nm (“ARC29A” manufactured by Bruwer Science) had beenformed was used as a substrate. For fabricating this underlayerantireflection film, “CLEAN TRACK ACT 8” (manufactured by Tokyo ElectronLtd.) was used.

Subsequently, the resin compositions shown in Tables 3 to 5 (Examples 1to 13, Examples 21 to 34, and Comparative Example 1) were subjected tospin coating onto the above-mentioned substrate using the “CLEAN TRACKACT 8” and baking (PB) under the conditions shown in Tables 6 and 7 toform resist films with a thickness of 205 nm. The resist films wereexposed to radiation through a patterned mask using an ArF excimer laserexposure apparatus (“NSR S306C” manufactured by Nicon Corp.,illuminating conditions: NA=0.78, sigma=0.93/0.69). After that, PEB wascarried out under the conditions shown in Tables 6 and 7. The resistfilm was developed at 23° C. for 30 seconds in a tetramethylammoniumhydroxide aqueous solution at a concentration of 2.38% by weight, washedwith water, and dried to form a positive-tone resist pattern. An optimumexposure dose at which a 1:1 line-and-space (1L1S) pattern with a linewidth of 90 nm was formed was taken as sensitivity (i). A scanningelectron microscope (“S-9380” manufactured by Hitachi High-TechnologiesCorporation) was used for the measurement.

(4) Cross-Sectional Shape (i) of Pattern

The cross-sectional shape of a line-and-space pattern with a line widthof 90 nm obtained in (3) above was inspected using “S-4800” manufacturedby Hitachi High-Technologies Corporation to measure the line width Lb atthe middle of the resist pattern and the line width La at the upper partof the film according to FIG. 2. The criteria was determined as “Good”when 0.9≤(La−Lb)/Lb≤1.1 was satisfied, and otherwise as “Bad”.

(5) Sensitivity (ii) (Liquid Immersion Lithography)

A 12-inch silicon wafer on which an underlayer antireflection film witha thickness of 77 nm (“ARC29A” manufactured by Bruwer Science) had beenformed was used as a substrate. For fabricating this underlayerantireflection film, “CLEAN TRACK ACT 12” (manufactured by TokyoElectron Ltd.) was used.

Subsequently, the resin compositions shown in Tables 4 and 5 (Examples14 and 15, and Comparative Example 2) were subjected to spin coatingonto the above-mentioned substrate using the “CLEAN TRACK ACT 12” andbaking (PB) under the conditions shown in Table 8 to form resist filmswith a thickness of 120 nm. The resist films were exposed to radiationthrough a patterned mask under the conditions of NA=0.85, σ₀/σ₁=0.96/0.7and dipole illumination using an ArF excimer laser liquid immersionexposure apparatus (“ASML AT1250i” manufactured by ASML). Pure water wasused as an immersion liquid medium between the resist surface and thelens of the liquid immersion lithographic instrument. After that, PEBwas carried out under the conditions shown in Table 8. The resist filmwas developed at 23° C. for 60 seconds in a tetramethylammoniumhydroxide aqueous solution at a concentration of 2.38% by weight, washedwith water, and dried to form a positive-tone resist pattern. An optimumexposure dose at which a 1:1 line-and-space (1L1S) pattern with a linewidth of 65 nm was formed was taken as sensitivity (ii). A scanningelectron microscope (“S-9380” manufactured by Hitachi High-TechnologiesCorporation) was used for the measurement.

(6) Depth of Focus (DOF)

A line-and-space pattern (1L1S) with a line width of 65 nm was formed inthe same manner as in (5) above. In this instance, the exposure doserequired for forming the line-and-space pattern having 1:1 line width,which is the depth of focus performance (DOF performance) at thesensitivity (optimal exposure dose) shown in Table 8, was measured usingscanning electron microscope (“S-9380” manufactured by HitachiHigh-Technologies Corporation).

(7) Cross-Sectional Shape (ii) of Pattern (Liquid Immersion Lithography)

The cross-sectional shape of a line-and-space pattern with a line widthof 65 nm obtained in the same manner as (5) above was inspected using“S-4800” manufactured by Hitachi High-Technologies Corporation tomeasure the line width Lb at the middle of the resist pattern and theline width La at the upper part of the film according to FIG. 2. Thecriteria was determined as “Good” when 0.9≤(La−Lb)/Lb≤1.1 was satisfied,and otherwise as “Bad”.

(8) Number of Defects (Number of Small Bridge-Type Defects and Number ofWatermark Defects)

A 12-inch silicon wafer on which an underlayer antireflection film witha thickness of 77 nm (“ARC29A” manufactured by Bruwer Science) had beenformed was used as a substrate. For fabricating this underlayerantireflection film, “CLEAN TRACK ACT 12” (manufactured by TokyoElectron Ltd.) was used.

Subsequently, the resin compositions shown in Tables 4 and 5 (Examples14 and 15, and Comparative Example 2) were subjected to spin coatingonto the above-mentioned substrate using the “CLEAN TRACK ACT 12” andbaking (PB) under the conditions shown in Table 8 to form resist filmswith a thickness of 150 nm. The resist films were exposed to radiationthrough a patterned mask under the conditions of NA=0.85,σ₀/σ₁=0.96/0.76 and annular illumination using an ArF excimer laserliquid immersion exposure apparatus (“ASML AT1250i” manufactured byASML). Pure water was used as an immersion liquid medium between theresist surface and the lens of the liquid immersion lithographicinstrument. After that, PEB was carried out under the conditions shownin Table 8. The resist film was developed at 23° C. for 60 seconds in atetramethylammonium hydroxide aqueous solution at a concentration of2.38% by weight, washed with water, and dried to form a positive-toneresist pattern. An optimum exposure dose at which a 1:1 line-and-space(1L1S) pattern with a line width of 100 nm was formed was taken assensitivity. A scanning electron microscope (“S-9380” manufactured byHitachi High-Technologies Corporation) was used for the measurement.

After that, the number of defects on the line-and-space (1L1S) patternwith a line width of 100 nm was measured using “KLA2351” manufactured byKLA-Tencor Corp. In addition, the defects measured by “KLA2351” wereobserved using a scanning electron microscope (“S-9380” manufactured byHitachi High Technologies Corp.) to classify the defects into smallbridge-type defects and watermark defects which is thought to beoriginating from exposure to ArF excimer laser by liquid immersionlithography. The results were shown in Table 8. The small bridge-typedefect is a type of defect that can be observed in normal exposure toArF excimer laser without filling the space between the resist surfaceand the lens.

(9) Sensitivity (iii)

A 12-inch silicon wafer on which an underlayer antireflection film witha thickness of 77 nm (“ARC29A” manufactured by Bruwer Science) had beenformed was used as a substrate. For fabricating this underlayerantireflection film, “CLEAN TRACK ACT 12” (manufactured by TokyoElectron Ltd.) was used.

Subsequently, the resin compositions shown in Table 4 (Examples 16 to20) were subjected to spin coating onto the above-mentioned substrateusing the “CLEAN TRACK ACT 12” and baking (PB) under the conditionsshown in Table 9 to form resist films with a thickness of 120 nm. Theresist films were exposed to radiation through a patterned mask underthe conditions of NA=0.85, σ₀/σ₁=0.96/0.76 and dipole illumination usingan ArF excimer laser liquid immersion exposure apparatus (“ASML AT1250i”manufactured by ASML). Pure water was used as an immersion liquid mediumbetween the resist surface and the lens of the liquid immersionlithographic instrument. After that, PEB was carried out under theconditions shown in Table 9. The resist film was developed at 23° C. for60 seconds in a tetramethylammonium hydroxide aqueous solution at aconcentration of 2.38% by weight, washed with water, and dried to form apositive-tone resist pattern. An optimum exposure dose at which a 1:1line-and-space (1L1S) pattern with a line width of 75 nm was formed wastaken as sensitivity. A scanning electron microscope (“S-9380”manufactured by Hitachi High-Technologies Corporation) was used for themeasurement.

(10) Cross-Sectional Shape (iii) of Pattern

The cross-sectional shape of a line-and-space pattern with a line widthof 75 nm obtained in (9) above was inspected using “S-4800” manufacturedby Hitachi High-Technologies Corporation to measure the line width Lb atthe middle of the resist pattern and the line width La at the upper partof the film according to FIG. 2. The criteria was determined as “Good”when 0.9≤(La−Lb)/Lb≤1.1 was satisfied, and otherwise as “Bad”.

(11) Exposure Margin (EL)

A 12-inch silicon wafer on which an underlayer antireflection film witha thickness of 77 nm (“AR46” manufactured by Rohm and Haas) had beenformed was used as a substrate. For fabricating this underlayerantireflection film, “CLEAN TRACK ACT 8” (manufactured by Tokyo ElectronLtd.) was used.

Subsequently, the resin compositions shown in Table 4 (Examples 16 to20) were subjected to spin coating onto the above-mentioned substrateusing the “CLEAN TRACK ACT 8” (manufactured by Tokyo Electron Ltd.) andbaking (PB) under the conditions shown in Table 9 to form resist filmswith a thickness of 160 nm. The resist films were exposed to radiationthrough a patterned mask under the conditions of NA=0.78,σ₀/σ₁=0.90/0.47 and dipoleX illumination using an ArF excimer laserexposure apparatus (“Nikon NSR S306C” manufactured by Nicon Corp.).After that, PEB was carried out under the conditions shown in Table 9.The resist film was developed at 23° C. for 60 seconds in atetramethylammonium hydroxide aqueous solution at a concentration of2.38% by weight, washed with water, and dried to form a positive-toneresist pattern. The exposure margin (EL) was determined by dividing thedifference of the exposure dose at which a pattern with a line width of75 nm−10% was formed and the exposure dose at which a pattern with aline width of 75 nm+10% was formed by the exposure dose at which apattern with a line width of 75 nm, in the line-and-space (1L1S)pattern-forming experiment with a line width of 75 nm. The exposuremargin (EL) was evaluated as “Bad” when the value was less than 9%, andas “Good” when 10% or more. A scanning electron microscope (“S-9380”manufactured by Hitachi High-Technologies Corporation) was used for themeasurement.

(12) Collapsing Margin

The collapsing margin was determined by dividing the maximum exposuredose that can maintain the line at the center of the pattern withoutcollapsing by the exposure dose for forming a 1:1 line-and-space (1L1S)pattern with a line width of 75 nm, in the line-and-space (1L1S)pattern-forming experiment with a line width of 75 nm. The collapsingmargin was evaluated as “Bad” when the resulting value was 1.1 or less,and as “Good” when the value was 1.2 or more. A scanning electronmicroscope (“S-9380” manufactured by Hitachi High-TechnologiesCorporation) was used for the measurement.

TABLE 6 Receding Sensitivity Patten Bake PEB contact angle (i) shape(temperature/time) (temperature/time) Elution (degree) (mJ/cm²) (i)Example 1 120° C./60 s 115° C./60 s Good 90.1 22 Good Example 2 120°C./60 s 115° C./60 s Good 73.1 22 Good Example 3 120° C./60 s 115° C./60s Good 85.3 22 Good Example 4 120° C./60 s 115° C./60 s Good 89.4 22Good Example 5 120° C./60 s 115° C./60 s Good 86.7 22 Good Example 6120° C./60 s 115° C./60 s Good 94.0 22 Good Example 7 120° C./60 s 115°C./60 s Good 84.8 22 Good Example 8 120° C./60 s 115° C./60 s Good 86.022 Good Example 9 120° C./60 s 115° C./60 s Good 80.0 22 Good Example 10120° C./60 s 115° C./60 s Good 86.7 30 Good Example 11 120° C./60 s 115°C./60 s Good 86.7 22 Good Example 12 120° C./60 s 115° C./60 s Good 86.722 Good Example 13 120° C./60 s 115° C./60 s Good 84.3 22 Good

TABLE 7 Receding Sensitivity Patten Bake PEB contact angle (i) shape(temperature/time) (temperature/time) Elution (degree) (mJ/cm²) (i)Example 21 100° C./60 s 110° C./60 s Good 80.0 52 Good Example 22 100°C./60 s 110° C./60 s Good 80.0 46 Good Example 23 110° C./60 s 110°C./60 s Good 80.0 54 Good Example 24 110° C./60 s 110° C./60 s Good 80.045 Good Example 25 115° C./60 s 115° C./60 s Good 86.0 37 Good Example26 115° C./60 s 115° C./60 s Good 80.0 52 Good Example 27 115° C./60 s115° C./60 s Good 81.0 49 Good Example 28 110° C./60 s 115° C./60 s Good80.0 33 Good Example 29 100° C./60 s 115° C./60 s Good 80.0 37 GoodExample 30 100° C./60 s 115° C./60 s Good 80.0 37 Good Example 31 130°C./60 s 120° C./60 s Good 86.0 33 Good Example 32 130° C./60 s 120°C./60 s Good 83.0 33 Good Example 33 120° C./60 s 105° C./60 s Good 80.043 Good Example 34 110° C./60 s 105° C./60 s Good 80.0 35 GoodComparative 120° C./60 s 115° C./60 s Bad 58.0 22 Good Example 1

TABLE 8 Receding Sensitivity Depth of Patten Bake PEB contact angle (ii)focus shape Defect (temperature/time) (temperature/time) Elution(degree) (mJ/cm²) (nm) (ii) Bridge Watermark Example 14 100° C./60 s130° C./60 s Good 86.7 24 500 Good 37 2 Example 15 100° C./60 s 130°C./60 s Good 83.3 25 500 Good 28 2 Comparative 100° C./60 s 130° C./60 sBad 57.6 24 500 Good 37 28 Example 2

TABLE 9 Receding Sensitivity Patten Bake PEB contact angle (iii)Collapsing shape (temperature/time) (temperature/time) Elution (degree)(mJ/cm²) EL margin (iii) Example 16 120° C./60 s 115° C./60 s Good 78.149.14 Good Good Good Example 17 120° C./60 s 115° C./60 s Good 78.249.22 Good Good Good Example 18 120° C./60 s 115° C./60 s Good 80.752.18 Good Good Good Example 19 120° C./60 s 115° C./60 s Good 80.950.52 Good Good Good Example 20 120° C./60 s 115° C./60 s Good 81.545.02 Good Good Good

As can be seen from Tables 6 and 7, the radiation-sensitive resincomposition for liquid immersion lithography to which thefluorine-containing polymer (A) of the present invention is addedproduces a resist film which elutes only a small amount of components inthe liquid with which the resist comes in contact upon liquid immersionlithography, provides a high receding contact angle, and produces anexcellent pattern shape. The resin composition is expected to play animportant role in the lithographic technology which is miniaturized inthe future.

In addition, as can be seen from the results shown in Table 8, theradiation-sensitive resin composition for liquid immersion lithographyto which the fluorine-containing polymer (A) of the present invention isadded produces a resist film which elutes only a small amount ofcomponents in the liquid with which the resist comes in contact uponliquid immersion lithography, provides a high receding contact angle,and exhibits excellent resist performance (sensitivity, depth of focus,pattern profile) in an experiment using an actual immersion scanningstepper. The resist film was confirmed to have an effect ofsignificantly reducing watermark defects which are through to beoriginating from an ArF immersion scanning stepper. In regard to bridgedefects resulting from the resist itself, there is no significantdifference between the resist made from the radiation-sensitive resincomposition for liquid immersion lithography of the present inventionand a general resist, indicating that the resin composition is suitablyused in liquid immersion lithography and is expected to play animportant role in the lithographic technology which is miniaturized inthe future.

Furthermore, as can be seen from the results shown in Table 9, theradiation-sensitive resin composition for liquid immersion lithographyto which the fluorine-containing polymer (A) of the present invention isadded produces a resist film which elutes only a small amount ofcomponents in the liquid with which the resist comes in contact uponliquid immersion lithography, provides a high receding contact angle,exhibits excellent resist performance (sensitivity, pattern profile) inan experiment using an actual immersion scanning stepper. The resistfilms were more excellent in the exposure margin and collapsing marginthan the resist films of Comparative Examples 1 and 2. It is thus shownthat the radiation-sensitive resin composition is suitably used inliquid immersion lithography and is expected to play an important rolein the lithographic technology which is miniaturized in the future.

The polymers (A-12) and (A-13) in Table 2 was purified by theliquid-liquid purification method described in (II) above. Thepurification method is thus evaluated to be suitably used in themanufacture of the resin.

The invention claimed is:
 1. A radiation-sensitive resin composition comprising: a fluorine-containing polymer consisting of: at least one first repeating unit represented by formula (1); and at least one second repeating unit represented by formula (2); an acid-unstable resin having an acid-unstable group, comprising a third repeating unit represented by formula (2); a radiation-sensitive acid generator; a nitrogen-containing compound; and a solvent,

wherein: R¹ represents a hydrogen atom, a methyl group or a trifluoromethyl group; A represents a single bond, an oxygen atom, a sulfur atom, a carbonyloxy group, an oxycarbonyl group, an amide group, a sulfonylamide group, or a urethane group; and R² represents a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms or a monovalent partially or fully fluorinated alicyclic hydrocarbon group having 4 to 20 carbon atoms,

wherein: R³ represents a hydrogen atom, a methyl group or a trifluoromethyl group; and each R⁴ individually represents a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof, or a linear or branched alkyl group having 1 to 4 carbon atoms, and optionally two of R⁴s taken together represent a divalent alicyclic hydrocarbon group or a derivative thereof together with the carbon atom to which the two of R⁴s bond, wherein an amount of the third repeating unit in the acid-unstable resin is from 53.8 to 69.6 mol % with respect to an amount of all repeating units in the acid-unstable resin.
 2. The radiation-sensitive resin composition according to claim 1, wherein the acid-unstable resin further comprises a repeating unit comprising a lactone structure.
 3. The radiation-sensitive resin composition according to claim 1, wherein the radiation-sensitive acid generator comprises an onium ion, the onium ion comprising: a cation; and an anion represented by R¹⁷C_(n)F_(2n)SO₃ ⁻, an anion represented by R¹⁷SO₃ ⁻, or both thereof, wherein R¹⁷ represents a fluorine atom, a cycloalkyl group, or a bridge alicyclic hydrocarbon group, the cycloalkyl group and the bridge alicyclic hydrocarbon group having no more than 12 carbon atoms and optionally being substituted, and n is an integer of 1 to
 10. 4. The radiation-sensitive resin composition according to claim 3, wherein the anion is represented by R¹⁷C_(n)F_(2n)SO₃ ⁻.
 5. The radiation-sensitive resin composition according to claim 3, wherein R¹⁷ is the bridge alicyclic hydrocarbon group.
 6. The radiation-sensitive resin composition according to claim 3, wherein the anion is represented by R¹⁷C_(n)F_(2n)SO₃ ⁻, and R¹⁷ is the bridge alicyclic hydrocarbon group.
 7. The radiation-sensitive resin composition according to claim 3, wherein the cation is represented by formula (7-1),

wherein R¹⁴ represents a hydrogen atom, a fluorine atom, a hydroxyl group, a linear or branched alkyl group having 1 to 10 carbon atoms, a linear or branched alkoxyl group having 1 to 10 carbon atoms, or a linear or branched alkoxycarbonyl group having 2 to 11 carbon atoms; R¹⁵ represents a linear or branched alkyl group having 1 to 10 carbon atoms, or an alkoxyl group; R¹⁶ individually represents a linear or branched alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group, or two R¹⁶s taken together represent a substituted or unsubstituted divalent group which comprises 2 to 10 carbon atoms; k is an integer of 0 to 2; and r is an integer of 0 to
 10. 8. The radiation-sensitive resin composition according to claim 7, wherein R¹⁶ individually represents a substituted or unsubstituted phenyl group or a substituted or unsubstituted naphthyl group.
 9. The radiation-sensitive resin composition according to claim 1, wherein an amount of the radiation-sensitive acid generator is from 0.5 to 10 parts by weight based on 100 parts by weight of a total of the fluorine-containing polymer and the acid-unstable resin.
 10. The radiation-sensitive resin composition according to claim 1, wherein a content of the fluorine-containing polymer in the radiation-sensitive resin composition is 0.1% or more by weight based on 100% by weight of the radiation-sensitive resin composition.
 11. The radiation-sensitive resin composition according to claim 1, wherein a content of the fluorine-containing polymer in the radiation-sensitive resin composition is from 0.5% to 35% by weight based on 100% by weight of the radiation-sensitive resin composition.
 12. The radiation-sensitive resin composition according to claim 1, wherein the fluorine-containing polymer has a weight average molecular weight determined by gel permeation chromatography in a range from 1,000 to 50,000.
 13. The radiation-sensitive resin composition according to claim 1, wherein the nitrogen-containing compound comprises at least one of an amine compound, an amide group-containing compound, a urea compound, or a nitrogen-containing heterocyclic compound.
 14. The radiation-sensitive resin composition according to claim 1, wherein an amount of the radiation-sensitive acid generator is from 7 to 9.5 parts by weight based on 100 parts by weight of the acid-unstable resin. 